What are cosmic rays? Cosmic rays: composition and origin What are cosmic rays

COSMIC RAYS, Streams of high-energy charged particles that come to the Earth from all directions from outer space and constantly bombard its atmosphere. The composition of cosmic rays is dominated by protons; there are also electrons, helium nuclei and heavier chemical elements (up to nuclei with charge Z ≈ 30). The most numerous nuclei in cosmic rays are hydrogen and helium atoms (≈85 and ≈10%, respectively). The share of other nuclei is small (does not exceed ≈5%). A small part of cosmic rays consists of electrons and positrons (less than 1%). Cosmic radiation incident on the boundary of the earth's atmosphere includes all stable charged particles and nuclei with lifetimes of the order of 10 6 years or more. Essentially, only particles accelerated in distant astrophysical sources can be called truly “primary” cosmic rays, and “secondary” particles can be called particles formed during the interaction of primary cosmic rays with interstellar gas. Thus, electrons, protons and helium nuclei, as well as carbon, oxygen, iron, etc., synthesized in stars are primary. On the contrary, the nuclei of lithium, beryllium and boron should be considered secondary. Antiprotons and positrons are partially, if not completely, secondary, but that portion of them that may be of primary origin is currently the subject of research.

History of cosmic ray research

In the beginning. 20th century in experiments with electroscopes and ionization chambers a constant residual ionization of gases was discovered, caused by some kind of penetrating radiation. Unlike radiation from environmental radioactive substances, penetrating radiation could not be stopped even by thick layers of lead. The extraterrestrial nature of the detected penetrating radiation was established in 1912 (W. Hess, Nobel Prize, 1936) in experiments with ionization chambers on balloons. It was found that with increasing distance from the Earth's surface, ionization caused by penetrating radiation increases. Its extraterrestrial origin was finally proven by R. Milliken in 1923–26 in experiments on the absorption of radiation by the atmosphere (it was he who coined the term “cosmic rays”).

The nature of cosmic rays up to the 1940s. remained unclear. During this time, the nuclear direction of cosmic ray research (nuclear physics aspect) was intensively developed - the study of the interaction of cosmic rays with matter, the formation of secondary particles and their absorption in the atmosphere. These studies, carried out using telescopes, counters, Wilson cameras and nuclear photographic emulsions (raised on balloons into the stratosphere), led, in particular, to the discovery of new elementary particles - positron (1932), muon(1936), π-meson (1947).

Systematic studies of the influence of the geomagnetic field on the intensity and direction of arrival of primary cosmic rays have shown that the vast majority of cosmic ray particles have a positive charge. This is associated with the east-west asymmetry of cosmic rays: due to the deflection of charged particles in the Earth's magnetic field, more particles come from the west than from the east. The use of photographic emulsions made it possible to establish the nuclear composition of primary cosmic rays (1948): traces of nuclei of heavy chemical elements, including iron, were discovered. Primary electrons in cosmic rays were first detected only in 1961 in stratospheric measurements.

From the end 1940s The problems of the origin and temporal variations of cosmic rays (cosmophysical aspect) came to the fore.

Characteristics and classification of cosmic rays

Cosmic rays resemble highly rarefied relativistic gas, whose particles practically do not interact with each other, but experience rare collisions with matter in the interstellar and interplanetary media and are exposed to cosmic magnetic fields. Cosmic ray particles have enormous kinetic energies (up to E kin ~ 10 21 eV). Near the Earth, the overwhelming majority of the cosmic ray flux consists of particles with energies from 10 6 eV to 10 9 eV, then the cosmic ray flux sharply weakens. Thus, at an energy of ~10 12 eV, no more than 1 particle/(m 2 ∙s) falls on the atmospheric boundary, and at Ekin ~ 10 15 eV – only 1 particle/(m 2 ∙year). This causes certain difficulties in studying cosmic rays of high and ultra-high (extreme) energies. Although the total flux of cosmic rays near the Earth is small (only about 1 particle/(cm 2 ∙s)), their energy density (about 1 eV/cm 3) within our Galaxy is comparable to the energy density of the total electromagnetic radiation of stars, thermal energy the movement of interstellar gas and the kinetic energy of its turbulent movements, as well as the energy density of the galactic magnetic field. It follows that cosmic rays must play an important role in many astrophysical processes.

Another important feature of cosmic rays is the non-thermal origin of their energy. Indeed, even at a temperature of ~10 9 K, apparently close to the maximum for stellar interiors, the average energy of thermal motion of particles is ≈3∙10 5 eV. The majority of cosmic ray particles observed near the Earth have the energy of St. 10 8 eV. This means that cosmic rays acquire energy through acceleration in specific astrophysical processes of plasma and electromagnetic nature.

According to their origin, cosmic rays can be divided into several groups: 1) cosmic rays of galactic origin (galactic cosmic rays); their source is our Galaxy, in which particles are accelerated to energies of the order of 10 18 eV; 2) cosmic rays of metagalactic origin (metagalactic cosmic rays); they are formed in other galaxies and have the highest, ultra-relativistic energies (over 10 18 eV); 3) solar cosmic rays; are generated on or near the Sun during solar flares And coronal mass ejections; their energy ranges from 10 6 eV to light. 10 10 eV; 4) anomalous cosmic rays; are formed in the Solar System on the periphery of the heliosphere; particle energies are 1–100 MeV/nucleon.

According to the content of lithium, beryllium and boron nuclei, which are formed as a result of interactions of cosmic rays with atoms interstellar medium, it is possible to determine the amount of matter X through which cosmic rays passed while wandering in the interstellar medium. The X value is approximately 5–10 g/cm2. The wandering time of cosmic rays in the interstellar medium (or their lifetime) and the value of X are related by the relation X≈ ρvt, where ρ is the average density of the interstellar medium, amounting to ~10 - 24 g/cm 3, t is the wandering time of cosmic rays in this medium, v – particle speed. It is usually believed that the value v for ultrarelativistic cosmic rays is practically equal to the speed of light c, so that their lifetime is ca. 3·10 8 years. It is determined either by the release of cosmic rays from the Galaxy and its halo, or by their absorption due to inelastic interactions with the matter of the interstellar medium.

Invading the Earth's atmosphere, primary cosmic rays destroy the nuclei of the most common chemical elements in the atmosphere - nitrogen and oxygen - and give rise to a cascade process in which all currently known elementary particles participate, in particular secondary particles such as protons, neutrons, mesons, electrons, as well as γ-quanta and neutrinos. It is customary to characterize the path traveled by a particle of cosmic rays in the atmosphere before the collision by the amount of substance in grams contained in a column with a cross section of 1 cm 2, i.e., to express the path of particles in g/cm 2 of atmospheric substance. This means that after a beam of protons with an initial intensity I 0 passes through the atmosphere x (g/cm2), the number of protons that did not experience a collision will be equal to I = I 0 exp(–x /λ), where λ is the average path of the particle. For protons, which make up the bulk of primary cosmic rays, the range λ in air is ≈70 g/cm 2 , for helium nuclei λ ≈25 g/cm 2 , for heavier nuclei it is even less. Protons experience their first collision with the atmosphere at an average altitude of 20 km (x ≈70 g/cm2). The thickness of the atmosphere at sea level is equivalent to 1030 g/cm 2, i.e. corresponds to approximately 15 nuclear ranges for protons. It follows that the probability of reaching the Earth's surface without experiencing collisions is negligible for a primary particle. Therefore, on the surface of the Earth, cosmic rays are detected only by weak ionization effects created by secondary particles.

Cosmic rays near the Earth

Cosmic rays of galactic and metagalactic origin occupy a huge energy range, covering approximately 15 orders of magnitude, from 10 6 to 10 21 eV. The energies of solar cosmic rays, especially during powerful solar flares, can reach large values, but the characteristic value of their energy usually does not exceed 10 9 eV. Therefore, the division of cosmic rays into galactic and solar ones is quite justified, since both the characteristics and sources of solar and galactic cosmic rays are completely different.

At energies below 10 GeV/nucleon, the intensity of galactic cosmic rays measured near the Earth depends on the level of solar activity (more precisely, on the interplanetary magnetic field changing during solar cycles). In the higher energy region, the intensity of galactic cosmic rays is almost constant over time. According to modern concepts, galactic cosmic rays themselves end in the energy region between 10 17 and 10 18 eV. The origin of cosmic rays of extremely high energies is most likely not connected with the Galaxy.

There are four ways to describe the spectra of various components of cosmic rays. 1. Number of particles per unit of hardness. The propagation (and probably also acceleration) of particles in cosmic magnetic fields depends on the Larmor radius r L or the magnetic rigidity of the particle R, which is the product of the Larmor radius and the magnetic field induction B: R = r L B = pc /(Ze), where p and Z are the momentum and charge of the particle (in units of electron charge e), c is the speed of light. 2. Number of particles per unit energy per nucleon. The fragmentation of nuclei propagating through interstellar gas depends on the energy per nucleon, since its amount is approximately conserved when the nucleus is destroyed by interaction with the gas. 3. Number of nucleons per unit of energy per nucleon. The generation of secondary particles in the atmosphere depends on the intensity of nucleons per unit energy per nucleon, almost regardless of whether the nucleons incident on the atmosphere are free protons or bound in nuclei. 4. Number of particles per unit of energy per nucleus. Experiments on widespread atmospheric showers, which use the atmosphere as a calorimeter, generally measure a quantity that is related to the total energy per particle. The units of measurement of the differential intensity of particles I have the form (cm –2 s –1 sr –1 E –1), where the energy E is represented in units of one of the four variables listed above.

The observed differential energy spectrum of cosmic rays in the energy region above 10 11 eV is shown in Fig. 1. The spectrum is described by a power law in a very wide energy range - from 10 11 to 10 20 eV with a slight change in slope of ca. 3·10 15 eV (kink, sometimes called “knee”) and approx. 10 19 eV (“ankle”, ankle). The integral flux of cosmic rays above the ankle is approximately 1 particle/(km 2 ·year).

Table 1. Relative content of various nuclei in galactic and solar cosmic rays, on the Sun and other stars (the content of oxygen nuclei is taken to be 1.0)

Core	Solar cosmic rays	Sun	Stars	Galactic cosmic rays
1H	4600 *	1445	925	685
2 He	70 *	91	150	48
3Li	?	<10 – 5	<10 – 5	0,3
4 Be – 5 B	0,02	<10 – 5	<10 – 5	0,8
6 C	0,54 *	0,60	0,26	1,8
7N	0,20	0,10	0,20	<0,8
8 O	1,0	1,0	1,0	1,0
9F	<0,03	10 – 3	<10 – 4	<0,1
10 Ne	0,16 *	0,054	0,36	0,30
11 Na	?	0,002	0,002	0,19
12 Mg	0,18 *	0,05	0,04	0,32
13 Al	?	0,002	0,004	0,06
14 Si	0,13 *	0,065	0,045	0,12
15P – 21Sc	0,06	0,032	0,024	0,13
16 S – 20 Ca	0,04 *	0,028	0,02	0,11
22 Ti – 28 Ni	0,02	0,006	0,033	0,28
26 Fe	0,15 *	0,05	0,06	0,14

* Observational data for the energy range 1–20 MeV/nucleon, the remaining data in this column refer to energies ≥ 40 MeV/nucleon. The error of most values ​​in the table is from 10 to 50%.

The intensity of primary nucleons in the energy range from several GeV to 10 TeV or slightly higher can be approximately described by the formula I N (E )≈1.8E –α nucleon/(cm 2 ∙s∙sr∙GeV), where E is the energy per nucleon (including rest energy), α ≈ (γ + 1) = 2.7 – differential spectrum index, γ – integral spectral index. OK. 79% of primary nucleons are free protons, approx. 70% of the remaining particles are nucleons bound in helium nuclei. Fractions (proportions) of primary nuclei are almost constant in the indicated energy range (possibly with small variations). In Fig. Figure 2 shows the spectrum of galactic cosmic rays in the energy region above ≈400 MeV/nucleon. The main components of cosmic rays are presented as a function of energy per nucleon for a certain epoch of the solar activity cycle. The quantity J(E) represents the number of particles having energies in the range from E to E + δE and passing through a unit surface per unit time per unit solid angle in a direction perpendicular to the surface.

Table 2. Intensity of galactic cosmic rays with total energy E≥ 2.5 GeV/nucleon outside the Earth’s magnetosphere near the minimum solar activity and differential spectrum parameters K A and γ for protons (H nucleus), α-particles (He nucleus) and various groups of nuclei

Core	Core charge Z	Intensity I(Z) at E≥ 2.5 GeV/nucleon, m –2 ∙s –1 ∙sr –1	Differential spectrum index γ	Spectrum constant K A	Interval E, GeV/nucleon
N	1	1300	2.4±0.1	4800	4,7–16
Not	2	88	2.5±0.2	360	2,5–800
Li, Be, B	3–5	1,9
C, N, O, F	6–9	5,6	2.6±0.1	25±5	2,4–8,0
Ne, Na, Mg, Al, Si, P, S, ...	≥10	2,5	2.6±0.15	12±2	2,4–8,0
Ca, Ti, Ni, Fe, ...	≥20	0,7

The relative abundance of various nuclei in galactic and solar cosmic rays, as well as (for comparison) in the Sun and other stars, is given in Table 1 for the region of relatively low energies (1–20 MeV/nucleon) and energies ≥ 40 MeV/nucleon. Table 2 summarizes the intensity data for higher energy galactic cosmic ray particles (≈2.5 GeV/nucleon). Table 3 contains the distribution of cosmic ray nuclei with an energy of ≈10.6 GeV/nucleon.

Table 3. Relative prevalence F cosmic ray nuclei at an energy of 10.6 GeV/nucleon (the content of oxygen nuclei is taken to be 1.0)

Core charge Z	Element	F
1	H	730
2	He	34
3–5	Li–B	0,4
6–8	C–O	2,2
9–10	F–Ne	0,3
11–12	Na–Mg	0,22
13–14	Al–Si	0,19
15–16	P–S	0,03
17–18	Cl–Ar	0,01
19–20	K–Ca	0,02
21–25	Sc–Mn	0,05
26–28	Fe–Ni	0,12

Methods for studying cosmic rays

Since cosmic ray particles differ in energy by a factor of 10–15, to study them it is necessary to use very diverse methods and instruments (Fig. 3, left). In this case, equipment installed on satellites and space rockets is widely used. In the Earth's atmosphere, measurements are carried out using small balloons and large high-altitude balloons, on its surface - using ground-based installations. Some of them reach sizes of hundreds of square kilometers and are located either high in the mountains, or deep underground, or at great depths in the ocean, where only high-energy secondary particles, such as muons, penetrate (Fig. 3, left). Continuous recording of cosmic rays on the Earth's surface has been carried out for more than 60 years by a worldwide network of stations for studying variations in cosmic rays - standard neutron monitors and muon telescopes. Valuable information about galactic and solar cosmic rays is provided by observations at large installations such as the Baksan complex for studying widespread atmospheric showers .

Nowadays, the main types of detectors that are used in the study of cosmic rays are photographic emulsions and X-ray films, ionization chambers, gas-discharge counters, neutron counters, Cherenkov and scintillation counters, solid-state semiconductor detectors, spark and drift chambers.

Nuclear physics studies of cosmic rays are carried out mainly using large-area counters for recording extensive air showers, discovered in 1938 (P. Auger). Showers contain a huge number of secondary particles, which are formed by the invasion of a single primary particle with an energy ≥ 10 15 eV. The main goal of such observations is to study the characteristics of an elementary act of nuclear interaction at high energies. Along with this, they provide information on the energy spectrum of cosmic rays at energies of 10 15 –10 20 eV, which is very important for searching for sources and mechanisms of cosmic ray acceleration.

The flux of particles with E ≈10 20 eV, studied by extensive air shower methods, is very small. For example, per 1 m 2 at the boundary of the atmosphere, only one particle with E ≈ 10 19 eV falls over 1 million years. To record such small flows, it is necessary to have large areas with detectors installed on them in order to register a sufficient number of events in a reasonable time. As of 2016, at giant installations for recording extensive air showers, various groups of scientists recorded, according to various estimates, from 10 to 20 events generated by particles with maximum energies of up to 3∙10 20 eV.

Observations in the cosmophysical aspect are carried out using very diverse methods depending on the energy of the particles. Variations of cosmic rays with energies of 10 9 –10 12 eV are studied using data from a worldwide network of neutron monitors, muon telescopes and other detectors. However, due to atmospheric absorption, ground-based installations are insensitive to particles with energy< 500 МэВ. Поэтому приборы для регистрации таких частиц поднимают на шарах-зондах в стратосферу до высот 30–35 км (рис. 3).

Extra-atmospheric measurements of the flux of cosmic rays with an energy of 1–500 MeV are carried out using geophysical rockets, satellites and other spacecraft (space probes). Direct observations of cosmic rays in interplanetary space, begun in the 1960s. in Earth orbit (near the ecliptic plane), since 1994 they have been carried out above the poles of the Sun (Ulysses spacecraft, "Ulysses") Space probes Voyager 1 and Voyager 2 ( Voyager 2, launched in 1977, has already reached the limits of the solar system. Thus, the first of these spacecraft crossed the boundary of the heliosphere in 2004, the second - in 2007. This happened, respectively, at distances of 94 AU. and 84 a.u. from the sun. As of 2016, both devices appear to be moving in a cloud of interstellar dust in which the Solar System is immersed.

The method of cosmogenic isotopes yielded a number of valuable results. They are formed by the interaction of cosmic rays with meteorites and cosmic dust, with the surface of the Moon and other planets, with the atmosphere or matter of the Earth. Cosmogenic isotopes carry information about past cosmic ray variations and solar-terrestrial connections. For example, based on the content of radiocarbon 14 C in tree rings ( radiocarbon dating method) it is possible to study variations in the intensity of cosmic rays over the past few thousand years. Using other long-lived isotopes (10 Be, 26 Al, 53 Mn, etc.) contained in meteorites, lunar soil, and deep-sea marine sediments, it is possible to reconstruct the picture of changes in the intensity of cosmic rays over the past millions of years.

With the development of space technology and radiochemical methods of analysis, it has become possible to study the characteristics of cosmic rays by their tracks (traces) in matter. Tracks are formed by cosmic ray nuclei in meteorites, lunar matter, in special target samples exposed on satellites and returned to Earth, in the helmets of astronauts who worked in outer space, etc. An indirect method is also used to study cosmic rays by ionization effects, caused by them in the lower part of the ionosphere, especially in polar latitudes (for example, the effect of increased absorption of short radio waves). In addition to ionization effects, cosmic rays also cause the formation of nitrogen oxides in the atmosphere. Together with precipitation (rain and snow), oxides are deposited and accumulate in the ice of Greenland and Antarctica for many years. Based on their content in ice columns (the so-called nitrate method), one can judge the intensity of cosmic rays in the past (tens and hundreds of years ago). These effects are significant mainly during the intrusion of solar cosmic rays into the atmosphere.

Origin of cosmic rays

Due to the high isotropy of cosmic rays, observations near the Earth do not allow us to determine where they are formed and how they are distributed in the Universe. Radio astronomy answered these questions for the first time in connection with the discovery of cosmic synchrotron radiation in the frequency range 10 7 –10 9 Hz. This radiation is created by electrons of very high energy (10 9 –10 10 eV) when they move in the magnetic fields of the Galaxy. Such electrons, which are one of the components of cosmic rays, occupy an extended region covering the entire Galaxy and is called the galactic halo. In interstellar magnetic fields, electrons move like other high-energy charged particles - protons and heavier nuclei. The only difference is that, due to their low mass, electrons, unlike heavier particles, intensively emit radio waves and thereby find themselves in distant parts of the Galaxy, being an indicator of cosmic rays.

In 1966, G. T. Zatsepin and V. A. Kuzmin (USSR) and K. Greisen (USA) suggested that the spectrum of cosmic rays at energies above 3·10 19 eV should be “cut off” (sharply bent) due to interaction high-energy particles with cosmic microwave background radiation (the so-called GZK effect). The registration of several events with energy E ≈10 20 eV can be explained if we assume that the sources of these particles are distant from us at a distance of no more than 50 Mpc. In this case, practically no interactions of cosmic rays with CMB photons occur due to the small number of photons on the path of the particle from the source to the observer. The first (preliminary) data obtained in 2007 within the framework of the large international “Auger Project” apparently for the first time indicate the existence of the GZK effect at E > 3·10 19 eV. In turn, this is an argument in favor of the metagalactic origin of cosmic rays with energies above 10 20 eV, which is significantly higher than the spectrum cutoff due to the GZK effect. Various ideas have been proposed to resolve the GZK paradox. One of the hypotheses is related to the possible violation of Lorentz invariance at ultra-high energies, in which neutral and charged π-mesons can be stable particles at energies above 10 19 eV and be part of primary cosmic rays.

In the beginning. 1970s The study of low-energy galactic cosmic rays carried out on spacecraft led to the discovery of an anomalous component of cosmic rays. It consists of incompletely ionized atoms of He, C, N, O, Ne and Ar. The anomaly is manifested in the fact that in the energy range from several units to several tens of MeV/nucleon, the spectrum of particles differs significantly from the spectrum of galactic cosmic rays (Fig. 4). An increase in the flux of particles is observed, which is believed to be associated with the acceleration of ions on the shock wave at the boundary of the heliomagnetosphere and the subsequent diffusion of these particles into the inner regions of the heliosphere. In addition, the abundance of anomalous cosmic ray elements differs significantly from the corresponding values ​​for galactic cosmic rays.

On the other hand, according to data for June 2008 obtained from the Voyager 1 spacecraft, an increase in the flux of cosmic rays of relatively low energies was noted (units - tens of MeV, Fig. 5). This first information about cosmic rays, obtained directly from the interstellar medium, raises new questions about the sources and nature (generation mechanisms) of the anomalous component of cosmic rays.

Mechanisms of cosmic ray acceleration

A complete theory of the acceleration of cosmic particles for the entire energy range in which they are observed has not yet been created. Even with regard to galactic cosmic rays, only models have been proposed that explain the most significant facts. These include, first of all, the energy density of cosmic rays (≈ 1 eV/cm 3), as well as the power-law form of their energy spectrum, which does not undergo any sharp changes up to an energy of ≈ 3 10 15 eV, where the index of the differential spectrum of all particles changes from –2.7 to –3.1.

Explosions are now considered the main source of galactic cosmic rays. supernovas. The requirements for the energy power of sources generating cosmic rays are very high (the generating power of cosmic rays should be on the order of 3·10 33 W), so that ordinary stars in the Galaxy cannot satisfy them. However, such power can be obtained from supernova explosions (V.L. Ginzburg, S.I. Syrovatsky, 1963). If during an explosion an energy of about 10 44 J is released, and explosions occur with a frequency of 1 time in 30–100 years, then their total power is about 10 35 W, and only a few percent of the energy of a supernova explosion is sufficient to provide the necessary power of cosmic rays.

At the same time, however, the question remains about the formation of the observed spectrum of galactic cosmic rays. The problem is that the macroscopic energy of the magnetized plasma (the expanding shell of the supernova) must be transferred to individual charged particles, providing an energy distribution that differs significantly from the thermal one. The most probable mechanism for the acceleration of galactic cosmic rays to an energy of the order of 10 15 eV (and possibly higher) seems to be the following. The movement of the shell ejected during the explosion generates a shock wave in the surrounding interstellar medium (Fig. 6). The diffusion propagation of charged particles captured in the acceleration process allows them to repeatedly cross the front of the shock wave (G. F. Krymsky, 1977). Each pair of successive intersections increases the energy of the particle in proportion to the energy already achieved (mechanism proposed by E. Fermi, 1949), which leads to acceleration of the particles. As the number of intersections of the shock wave front increases, the probability of leaving the acceleration region also increases, so that as the energy increases, the number of particles decreases approximately according to a power law, and the acceleration turns out to be very effective, and the spectrum of accelerated particles is very hard: µE –2.

Under certain model assumptions, the proposed scheme gives a maximum energy value E max ~ 10 17 Z eV, where Z is the charge of the accelerated nucleus. The calculated spectrum of cosmic rays up to the maximum achievable energy turns out to be very hard (µE –2). To compensate for the difference between the theoretical (–2) and experimental (–2.7) spectrum indices, a significant softening of the spectrum during cosmic ray propagation is required. Such mitigation can be achieved due to the energy dependence of the diffusion coefficient of particles as they move from sources to the Earth.

Among other acceleration mechanisms, in particular, acceleration on a standing shock wave during the rotation of a neutron star with a powerful magnetic field (~10 12 G) is discussed. The maximum energy of particles can reach (10 17 –10 18) Z eV, and the effective acceleration time can be 10 years. Particle acceleration is also possible in shock waves formed during galactic collisions. Such an event can occur with a frequency of approximately 1 time in 5·10 8 years; the maximum achievable energy in this case is estimated as 3·10 19 Z eV. The process of acceleration by shock waves in jets generated by active galactic nuclei leads to a similar assessment. Approximately the same estimates are given by models that consider acceleration by shock waves caused by the accretion of matter in galaxy clusters. The highest estimates (up to energies of the order of 10 21 eV) can be obtained within the framework of the model of the cosmological origin of gamma-ray bursts. Exotic scenarios are also discussed in which conventional particle acceleration is not required at all. In such scenarios, cosmic rays arise from the decay or annihilation of so-called. topological defects (cosmic strings, monopoles, etc.) that arose in the first moments of the expansion of the Universe.

Problems and prospects

The study of cosmic rays provides valuable information about electromagnetic fields in various regions of outer space. Information “recorded” and “transferred” by cosmic ray particles on their way to Earth is deciphered in the study of cosmic ray variations - spatiotemporal changes in the cosmic ray flux under the influence of dynamic, electromagnetic and plasma processes in interstellar space, inside the heliosphere (in the flux solar wind) and in the vicinity of the Earth (in the Earth's magnetosphere and atmosphere).

On the other hand, as a natural source of high-energy particles, cosmic rays play an indispensable role in studying the structure of matter and interactions between elementary particles. The energies of individual cosmic ray particles are so high that they will remain out of competition for a long time in comparison with particles accelerated by the most powerful laboratory accelerators. Thus, the maximum energy of particles (protons) obtained in most modern ground-based accelerators generally does not exceed 10 12 eV. Only on June 3, 2015 at CERN at the Large Hadron Collider it was possible for the first time to accelerate protons to energies of 1.3∙10 13 eV (with a designed maximum energy of 1.4∙10 13 eV).

Observations on various cosmic scales (Galaxy, Sun, Earth's magnetosphere, etc.) show that particle acceleration occurs in cosmic plasma wherever there are sufficiently intense inhomogeneous movements and magnetic fields. However, in large numbers and to very high energies, particles can only be accelerated where very large kinetic energy is imparted to the plasma. This is exactly what happens in such grandiose cosmic processes as supernova explosions, the activity of radio galaxies and quasars.

Significant progress has been made in understanding such processes over the past decades, but many questions remain. The situation remains particularly acute in the region of high and extremely high energies, where the quality of information (data statistics) still does not allow us to draw clear conclusions about the sources of cosmic rays and the mechanisms of their acceleration. It can be hoped that experiments at the Large Hadron Collider will provide information on hadronic interactions up to energies of ~10 17 eV and significantly reduce the current uncertainty that arises when extrapolating phenomenological models of hadronic interactions to the ultrahigh energy region. The next generation of extensive air shower facilities should provide precision studies of the energy spectrum and composition of cosmic rays in the energy region 10 17 –10 19 eV, where the transition from galactic cosmic rays to cosmic rays of extragalactic origin appears to occur.

Along with the huge role of cosmic rays in astrophysical processes, their importance is important for studying the distant past of the Earth (climate changes, evolution of the biosphere, etc.), as well as for solving some practical problems (for example, monitoring and forecasting space weather and ensuring radiation safety of astronauts).

In the beginning. 21st century The possible role of cosmic rays in atmospheric and climate processes is attracting increasing attention. Although the energy density of cosmic rays is small compared to the enormous energetics of various atmospheric processes, in some of them cosmic rays appear to play a decisive role. In the earth's atmosphere at altitudes less than 30 km, cosmic rays serve as the main source of ion formation. The processes of condensation and the formation of water droplets largely depend on the ion density. Thus, during decreases in the intensity of galactic cosmic rays in the region of solar wind disturbances in interplanetary space caused by solar flares (the so-called Forbush effect), cloudiness and precipitation levels decrease. After solar flares and the arrival of solar cosmic rays to Earth, the amount of cloudiness and precipitation levels increase. These changes in both the first and second cases are at least 10%. After the invasion of the polar regions of the Earth by large flows of accelerated particles from the Sun, a change in temperature is observed in the upper layers of the atmosphere. Cosmic rays are also actively involved in the formation of thunderstorm electricity. In the beginning. 21st century The influence of cosmic rays on ozone concentration and other processes in the atmosphere is being intensively studied.

All of these effects are studied in detail within the framework of a more general problem. solar-terrestrial connections. Of particular interest is the development of the mechanisms of these connections. In particular, this applies to the trigger mechanism, in which an energetically weak primary impact on an unstable system leads to a multiple increase in secondary effects, for example, to the development of a powerful cyclone.

Material from Wikipedia - the free encyclopedia

Cosmic rays- elementary particles and atomic nuclei moving with high energies in outer space.

Basic information

Cosmic ray physics considered to be part high energy physics And particle physics.

Physics of cosmic rays studies:

• processes leading to the emergence and acceleration of cosmic rays;
• cosmic ray particles, their nature and properties;
• phenomena caused by cosmic ray particles in outer space, the atmosphere of the Earth and planets.

Studying the flows of high-energy charged and neutral cosmic particles falling on the boundary of the Earth's atmosphere is the most important experimental task.

Classification according to the origin of cosmic rays:

• outside our Galaxy
• in the Galaxy
• in the sun
• in interplanetary space

Primary It is customary to call extragalactic and galactic rays. Secondary It is customary to call particle flows passing and transforming in the Earth’s atmosphere.

Cosmic rays are a component of natural radiation (background radiation) on the Earth's surface and in the atmosphere.

Before the development of accelerator technology, cosmic rays served as the only source of high-energy elementary particles. Thus, the positron and muon were first found in cosmic rays.

The energy spectrum of cosmic rays consists of 43% energy from protons, another 23% from helium energy (alpha particles) and 34% energy transferred by other particles.

By particle number, cosmic rays are 92% protons, 6% helium nuclei, about 1% heavier elements, and about 1% electrons. When studying sources of cosmic rays outside the Solar System, the proton-nuclear component is mainly detected by the flux of gamma rays it creates by orbital gamma-ray telescopes, and the electron component is detected by the synchrotron radiation it generates, which occurs in the radio range (in particular, at meter waves - at radiation in the magnetic field of the interstellar medium), and with strong magnetic fields in the region of the cosmic ray source - and to higher frequency ranges. Therefore, the electronic component can also be detected by ground-based astronomical instruments.

Traditionally, particles observed in cosmic rays are divided into the following groups: $p\; (Z=1),\; \backslash alpha\; (Z=2),\; L\; (Z=3-5),\; M\; (Z=6-9),\; H\; (Z\; \backslash geqslant\; 10),\; VH\; (Z\; \backslash geqslant\; 20)$(respectively, protons, alpha particles, light, medium, heavy and superheavy). A feature of the chemical composition of primary cosmic radiation is the anomalously high (several thousand times) content of group L nuclei (lithium, beryllium, boron) compared to the composition of stars and interstellar gas. This phenomenon is explained by the fact that the mechanism of generation of cosmic particles primarily accelerates heavy nuclei, which, when interacting with protons of the interstellar medium, decay into lighter nuclei. This assumption is confirmed by the fact that cosmic rays have a very high degree of isotropy.

History of cosmic ray physics

The first indication of the possibility of the existence of ionizing radiation of extraterrestrial origin was obtained at the beginning of the 20th century in experiments studying the conductivity of gases. The detected spontaneous electric current in the gas could not be explained by ionization arising from the natural radioactivity of the Earth. The observed radiation turned out to be so penetrating that a residual current was still observed in the ionization chambers, shielded by thick layers of lead. In 1911-1912, a number of experiments were carried out with ionization chambers on balloons. Hess discovered that radiation increases with altitude, whereas ionization caused by the radioactivity of the Earth should decrease with altitude. Colherster's experiments proved that this radiation is directed from top to bottom.

In 1921-1925, the American physicist Millikan, studying the absorption of cosmic radiation in the Earth's atmosphere depending on the observation altitude, discovered that in lead this radiation is absorbed in the same way as gamma radiation from nuclei. Millikan was the first to call this radiation cosmic rays. In 1925, Soviet physicists L.A. Tuvim and L.V. Mysovsky measured the absorption of cosmic radiation in water: it turned out that this radiation was absorbed ten times less than the gamma radiation of nuclei. Mysovsky and Tuwim also discovered that the intensity of radiation depends on barometric pressure - they discovered the “barometric effect”. D.V. Skobeltsyn's experiments with a cloud chamber placed in a constant magnetic field made it possible to “see”, due to ionization, traces (tracks) of cosmic particles. D. V. Skobeltsyn discovered showers of cosmic particles. Experiments in cosmic rays made it possible to make a number of fundamental discoveries for the physics of the microworld.

Solar cosmic rays

Solar cosmic rays (SCR) are energetic charged particles - electrons, protons and nuclei - injected by the Sun into interplanetary space. The SCR energy ranges from several keV to several GeV. At the lower end of this range, SCRs are confined to protons from high-speed solar wind streams. SCR particles appear as a result of solar flares.

Ultra-high energy cosmic rays

The energy of some particles exceeds the GZK (Greisen - Zatsepin - Kuzmin) limit - the theoretical energy limit for cosmic rays 5·10 19 eV, caused by their interaction with photons of the cosmic microwave background radiation. Several dozen such particles were recorded by the AGASA observatory over the course of a year. (English)Russian. These observations do not yet have a sufficiently substantiated scientific explanation.

Detection of cosmic rays

For a long time after the discovery of cosmic rays, the methods for registering them did not differ from the methods for registering particles in accelerators, most often gas-discharge counters or nuclear photographic emulsions raised into the stratosphere or into outer space. But this method does not allow systematic observations of high-energy particles, since they appear quite rarely, and the space in which such a counter can conduct observations is limited by its size.

Modern observatories operate on different principles. When a high-energy particle enters the atmosphere, it interacts with air atoms in the first 100 g/cm², giving rise to a flurry of particles, mainly pions and muons, which, in turn, give birth to other particles, and so on. A cone of particles is formed, which is called a shower. Such particles move at speeds exceeding the speed of light in air, resulting in Cherenkov glow, which is detected by telescopes. This technique makes it possible to monitor areas of the sky covering hundreds of square kilometers.

Implications for spaceflight

ISS astronauts, when they close their eyes, see flashes of light no more than once every 3 minutes; perhaps this phenomenon is associated with the impact of high-energy particles entering the retina. However, this has not been experimentally confirmed; it is possible that this effect has exclusively psychological foundations.

Long-term exposure to cosmic radiation can have a very negative impact on human health. For the further expansion of humanity to other planets of the solar system, reliable protection against such dangers should be developed - scientists from Russia and the USA are already looking for ways to solve this problem.

see also

• Observatory Pierre Auger ( English)

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Notes

1. // Physical encyclopedia / Ch. ed. A. M. Prokhorov. - M.: Great Russian Encyclopedia, 1990. - T. 2. Quality factor - Magneto-optics. - pp. 471-474. - 703 p. - ISBN 5852700614.
3. Ginzburg V.L. , Syrovatsky S.I. Current state of the question about the origin of cosmic rays // Physics Physics. - 1960. - No. 7.- P. 411-469. - ISSN 1996-6652. - URL: ufn.ru/ru/articles/1960/7/b/
4. , With. 18.
5. V. L. Ginzburg Cosmic rays: 75 years of research and prospects for the future // Earth and the Universe. - M.: Nauka, 1988. - No. 3. - P. 3-9.
7. , With. 236.

Literature

• S. V. Murzin. Introduction to cosmic ray physics. M.: Atomizdat, 1979.
• Model of outer space - M.: Moscow State University Publishing House, in 3 volumes.
• A. D. Filonenko(Russian) // UFN. - 2012. - T. 182. - pp. 793-827.
• Dorman L.I. Experimental and theoretical foundations of cosmic ray astrophysics. - M.: Nauka, 1975. - 464 p.
• ed. Shirkov D.V. Physics of the microworld. - M.: Soviet Encyclopedia, 1980. - 528 p.

Links

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Excerpt characterizing cosmic rays

At this time, Petya, to whom no one was paying attention, approached his father and, all red, in a breaking, sometimes rough, sometimes thin voice, said:
“Well, now, daddy, I will decisively say - and mummy too, whatever you want - I will decisively say that you will let me into military service, because I can’t ... that’s all ...
The Countess raised her eyes to the sky in horror, clasped her hands and angrily turned to her husband.
- So I agreed! - she said.
But the count immediately recovered from his excitement.
“Well, well,” he said. - Here’s another warrior! Stop the nonsense: you need to study.
- This is not nonsense, daddy. Fedya Obolensky is younger than me and is also coming, and most importantly, I still can’t learn anything now that ... - Petya stopped, blushed until he sweated and said: - when the fatherland is in danger.
- Complete, complete, nonsense...
- But you yourself said that we would sacrifice everything.
“Petya, I’m telling you, shut up,” the count shouted, looking back at his wife, who, turning pale, looked with fixed eyes at her youngest son.
- And I’m telling you. So Pyotr Kirillovich will say...
“I’m telling you, it’s nonsense, the milk hasn’t dried yet, but he wants to go into military service!” Well, well, I’m telling you,” and the count, taking the papers with him, probably to read them again in the office before resting, left the room.
- Pyotr Kirillovich, well, let’s go have a smoke...
Pierre was confused and indecisive. Natasha's unusually bright and animated eyes, constantly looking at him more than affectionately, brought him into this state.
- No, I think I’ll go home...
- It’s like going home, but you wanted to spend the evening with us... And then you rarely came. And this one of mine...” the count said good-naturedly, pointing at Natasha, “she’s only cheerful when she’s with you...”
“Yes, I forgot... I definitely need to go home... Things to do...” Pierre said hastily.
“Well, goodbye,” said the count, completely leaving the room.
- Why are you leaving? Why are you upset? Why?..” Natasha asked Pierre, looking defiantly into his eyes.
“Because I love you! - he wanted to say, but he didn’t say it, he blushed until he cried and lowered his eyes.
- Because it’s better for me to visit you less often... Because... no, I just have business.
- From what? no, tell me,” Natasha began decisively and suddenly fell silent. They both looked at each other in fear and confusion. He tried to grin, but could not: his smile expressed suffering, and he silently kissed her hand and left.
Pierre decided not to visit the Rostovs with himself anymore.

Petya, after receiving a decisive refusal, went to his room and there, locking himself away from everyone, wept bitterly. They did everything as if they had not noticed anything, when he came to tea, silent and gloomy, with tear-stained eyes.
The next day the sovereign arrived. Several of the Rostov courtyards asked to go and see the Tsar. That morning Petya took a long time to get dressed, comb his hair and arrange his collars like the big ones. He frowned in front of the mirror, made gestures, shrugged his shoulders and, finally, without telling anyone, put on his cap and left the house from the back porch, trying not to be noticed. Petya decided to go straight to the place where the sovereign was and directly explain to some chamberlain (it seemed to Petya that the sovereign was always surrounded by chamberlains) that he, Count Rostov, despite his youth, wanted to serve the fatherland, that youth could not be an obstacle for devotion and that he is ready... Petya, while he was getting ready, prepared many wonderful words that he would say to the chamberlain.
Petya counted on the success of his presentation to the sovereign precisely because he was a child (Petya even thought how everyone would be surprised at his youth), and at the same time, in the design of his collars, in his hairstyle and in his sedate, slow gait, he wanted to present himself as an old man. But the further he went, the more he was amused by the people coming and going at the Kremlin, the more he forgot to observe the sedateness and slowness characteristic of adult people. Approaching the Kremlin, he already began to take care that he would not be pushed in, and resolutely, with a threatening look, put his elbows out to his sides. But at the Trinity Gate, despite all his determination, people who probably did not know for what patriotic purpose he was going to the Kremlin, pressed him so hard against the wall that he had to submit and stop until the gate with a buzzing sound under the arches the sound of carriages passing by. Near Petya stood a woman with a footman, two merchants and a retired soldier. After standing at the gate for some time, Petya, without waiting for all the carriages to pass, wanted to move on ahead of the others and began to decisively work with his elbows; but the woman standing opposite him, at whom he first pointed his elbows, angrily shouted at him:
- What, barchuk, you are pushing, you see - everyone is standing. Why climb then!
“So everyone will climb in,” said the footman and, also starting to work with his elbows, he squeezed Petya into the stinking corner of the gate.
Petya wiped the sweat that covered his face with his hands and straightened his sweat-soaked collars, which he had arranged so well at home, like the big ones.
Petya felt that he had an unpresentable appearance, and was afraid that if he presented himself like that to the chamberlains, he would not be allowed to see the sovereign. But there was no way to recover and move to another place due to the cramped conditions. One of the passing generals was an acquaintance of the Rostovs. Petya wanted to ask for his help, but thought that it would be contrary to courage. When all the carriages had passed, the crowd surged and carried Petya out to the square, which was completely occupied by people. Not only in the area, but on the slopes, on the roofs, there were people everywhere. As soon as Petya found himself in the square, he clearly heard the sounds of bells and joyful folk talk filling the entire Kremlin.
At one time the square was more spacious, but suddenly all their heads opened, everything rushed forward somewhere else. Petya was squeezed so that he could not breathe, and everyone shouted: “Hurray! Hurray! hurray! Petya stood on tiptoes, pushed, pinched, but could not see anything except the people around him.
There was one common expression of tenderness and delight on all faces. One merchant's wife, standing next to Petya, was sobbing, and tears flowed from her eyes.
- Father, angel, father! – she said, wiping away tears with her finger.
- Hooray! - they shouted from all sides. For a minute the crowd stood in one place; but then she rushed forward again.
Petya, not remembering himself, clenched his teeth and brutally rolled his eyes, rushed forward, working with his elbows and shouting “Hurray!”, as if he was ready to kill himself and everyone at that moment, but exactly the same brutal faces climbed from his sides with the same shouts of “Hurray!”
“So this is what a sovereign is! - thought Petya. “No, I can’t submit a petition to him myself, it’s too bold!” Despite this, he still desperately made his way forward, and from behind the backs of those in front he glimpsed an empty space with a passage covered with red cloth; but at that time the crowd wavered back (in front the police were pushing away those who were advancing too close to the procession; the sovereign was passing from the palace to the Assumption Cathedral), and Petya unexpectedly received such a blow to the side in the ribs and was so crushed that suddenly everything in his eyes became blurred and he lost consciousness. When he came to his senses, some kind of clergyman, with a bun of graying hair back, in a worn blue cassock, probably a sexton, held him under his arm with one hand, and with the other protected him from the pressing crowd.
- The youngster was run over! - said the sexton. - Well, that’s it!.. it’s easier... crushed, crushed!
The Emperor went to the Assumption Cathedral. The crowd smoothed out again, and the sexton led Petya, pale and not breathing, to the Tsar’s cannon. Several people took pity on Petya, and suddenly the whole crowd turned to him, and a stampede began around him. Those who stood closer served him, unbuttoned his frock coat, placed a gun on the dais and reproached someone - those who crushed him.
“You can crush him to death this way.” What is this! To do murder! “Look, cordial, he’s become white as a tablecloth,” said the voices.
Petya soon came to his senses, the color returned to his face, the pain went away, and for this temporary trouble he received a place on the cannon, from which he hoped to see the sovereign who was about to return. Petya no longer thought about submitting a petition. If only he could see him, he would consider himself happy!
During the service in the Assumption Cathedral - a combined prayer service on the occasion of the arrival of the sovereign and a prayer of thanks for the conclusion of peace with the Turks - the crowd spread out; Shouting sellers of kvass, gingerbread, and poppy seeds appeared, which Petya was especially keen on, and ordinary conversations could be heard. One merchant's wife showed her torn shawl and said how expensive it was bought; another said that nowadays all silk fabrics have become expensive. The sexton, Petya’s savior, was talking with the official about who and who was serving with the Reverend today. The sexton repeated the word soborne several times, which Petya did not understand. Two young tradesmen joked with the courtyard girls gnawing nuts. All these conversations, especially jokes with girls, which had a special attraction for Petya at his age, all these conversations did not interest Petya now; ou sat on his gun dais, still worried at the thought of the sovereign and his love for him. The coincidence of the feeling of pain and fear when he was squeezed with a feeling of delight further strengthened in him the awareness of the importance of this moment.
Suddenly, cannon shots were heard from the embankment (they were firing to commemorate peace with the Turks), and the crowd quickly rushed to the embankment to watch them shoot. Petya also wanted to run there, but the sexton, who had taken the little bark under his protection, did not let him in. The shots still continued when officers, generals, and chamberlains ran out of the Assumption Cathedral, then others came out not so hastily, the caps were taken off their heads again, and those who had run away to look at the cannons ran back. Finally, four more men in uniforms and ribbons emerged from the cathedral doors. "Hooray! Hooray! – the crowd shouted again.
- Which? Which? - Petya asked around him in a crying voice, but no one answered him; everyone was too carried away, and Petya, choosing one of these four faces, whom he could not clearly see because of the tears that had come into his eyes with joy, concentrated all his delight on him, although it was not the sovereign, shouted “Hurray! in a frantic voice and decided that tomorrow, no matter what it cost him, he would be a military man.
The crowd ran after the sovereign, accompanied him to the palace and began to disperse. It was already late, and Petya had not eaten anything, and sweat poured from him like hail; but he did not go home and, together with a diminished, but still quite large crowd, stood in front of the palace, during the sovereign’s dinner, looking out the palace windows, expecting something else and equally envying the dignitaries who were driving up to the porch - for the sovereign’s dinner, and the chamber lackeys who served at the table and flashed through the windows.
At the sovereign’s dinner, Valuev said, looking out the window:
“The people still hope to see your Majesty.”
Lunch was already over, the sovereign got up and, finishing his biscuit, went out onto the balcony. The people, with Petya in the middle, rushed to the balcony.
-Angel, father! Hurray, father!.. - the people and Petya shouted, and again the women and some weaker men, including Petya, began to cry with happiness. A rather large piece of the biscuit, which the sovereign was holding in his hand, broke off and fell onto the railing of the balcony, from the railing to the ground. The driver standing closest to him in his undershirt rushed to this piece of biscuit and grabbed it. Some of the crowd rushed to the coachman. Noticing this, the sovereign ordered a plate of biscuits to be served and began throwing biscuits from the balcony. Petya's eyes became bloodshot, the danger of being crushed excited him even more, he threw himself on the biscuits. He didn’t know why, but he had to take one biscuit from the king’s hands, and he had to not give in. He rushed and knocked down an old woman who was catching a biscuit. But the old woman did not consider herself defeated, although she was lying on the ground (the old woman was catching the biscuits and did not get them with her hands). Petya knocked her hand away with his knee, grabbed the biscuit and, as if afraid of being late, again shouted “Hurray!”, in a hoarse voice.
The Emperor left, and after that most of the people began to disperse.
“I said that we would have to wait a little longer, and so it happened,” people said joyfully from different sides.
No matter how happy Petya was, he was still sad to go home and know that all the pleasure of that day was over. From the Kremlin, Petya did not go home, but to his comrade Obolensky, who was fifteen years old and who also joined the regiment. Returning home, he resolutely and firmly announced that if they didn’t let him in, he would run away. And the next day, although he had not yet completely given up, Count Ilya Andreich went to find out how to settle Petya somewhere safer.

On the morning of the 15th, the third day after this, countless carriages stood at the Slobodsky Palace.
The halls were full. In the first there were noblemen in uniforms, in the second there were merchants with medals, beards and blue caftans. There was a hum and movement throughout the hall of the Noble Assembly. At one large table, under the portrait of the sovereign, the most important nobles sat on chairs with high backs; but most of the nobles walked around the hall.
All the nobles, the same ones whom Pierre saw every day, either in the club or in their houses, were all in uniforms, some in Catherine’s, some in Pavlov’s, some in the new Alexander, some in the general noble, and this general character of the uniform gave something strange and fantastic to these old and young, the most diverse and familiar faces. Particularly striking were the old people, low-sighted, toothless, bald, covered in yellow fat or wrinkled and thin. For the most part, they sat in their seats and were silent, and if they walked and talked, they joined someone younger. Just like on the faces of the crowd that Petya saw in the square, on all these faces there was a striking feature of the opposite: a general expectation of something solemn and ordinary, yesterday - the Boston party, Petrushka the cook, Zinaida Dmitrievna’s health, etc.
Pierre, who had been wearing an awkward nobleman's uniform that had become too tight for him since early morning, was in the halls. He was excited: the extraordinary gathering of not only the nobility, but also the merchants - the estates, etats generaux - evoked in him a whole series of thoughts that had long been abandoned, but were deeply etched in his soul about the Contrat social [Social Contract] and the French Revolution. The words he noticed in the appeal that the sovereign would arrive in the capital to confer with his people confirmed him in this view. And he, believing that in this sense something important was approaching, something that he had been waiting for a long time, walked around, looked closely, listened to the conversation, but nowhere did he find the expression of the thoughts that occupied him.

COSMIC RAYS, a stream of high-energy charged particles that come to the Earth from all directions of outer space and constantly bombard its atmosphere. The composition of cosmic rays is dominated by protons; there are also electrons, nuclei of He and heavier chemical elements (up to nuclei with charge Z ≈ 30; see table). The most numerous nuclei in cosmic rays are H and He (about 85% and about 10%, respectively); the share of other nuclei is small (does not exceed 5%). A small part of cosmic rays consists of electrons and positrons (less than 1%). Cosmic radiation incident on the boundary of the earth's atmosphere contains all stable charged particles and nuclei with lifetimes of the order of 10 6 years or more. Essentially, only particles accelerated in distant astrophysical sources can be called truly “primary” cosmic rays, and “secondary” particles can be called particles formed during the interaction of primary cosmic rays. with interstellar gas. Thus, electrons, protons and nuclei of He, C, O, Fe, etc., synthesized in stars, are primary. On the contrary, the Li, Be and B nuclei should be considered secondary. Antiprotons and positrons are partly, if not entirely, secondary.

History of cosmic ray research. At the beginning of the 20th century, experiments with electroscopes and ionization chambers discovered a constant residual ionization of gases caused by some kind of penetrating radiation. Unlike radiation from environmental radioactive substances, penetrating radiation could not be stopped even by thick layers of lead. The extraterrestrial nature of the detected penetrating radiation was established in 1912 (W. Hess, Nobel Prize, 1936) in experiments with ionization chambers on balloons. It was found that with increasing distance from the Earth's surface, ionization caused by penetrating radiation increases. Its extraterrestrial origin was finally proven by R. Millikan in 1923-26 in experiments on the absorption of radiation by the atmosphere (it was he who coined the term “cosmic rays”).

The nature of cosmic rays remained unclear until the 1940s. During this time, the nuclear direction of cosmic ray research (nuclear physics aspect) was intensively developed - the study of the interaction of cosmic rays with matter, the formation of secondary particles and their absorption in the atmosphere. These studies, carried out with the help of counter telescopes, cloud chambers and nuclear photographic emulsions (lifted on sounding balloons into the stratosphere), led, in particular, to the discovery of new elementary particles - the positron (1932), the muon (1937), the π-meson (1947 ).

Systematic studies of the influence of the geomagnetic field on the intensity and direction of arrival of primary cosmic rays have shown that the vast majority of cosmic rays have a positive charge.

This is associated with the east-west asymmetry of cosmic rays: due to the deflection of charged particles in the Earth's magnetic field, more particles come from the west than from the east. The use of photographic emulsions made it possible to establish the nuclear composition of primary cosmic rays (1948): traces of nuclei of heavy elements, including iron, were discovered. Primary electrons in cosmic rays were first recorded in stratospheric measurements only in 1961.

Since the late 1940s, the problems of the origin and temporal variations of cosmic rays (cosmophysical aspect) have come to the fore.

General characteristics of cosmic rays. Cosmic rays resemble highly rarefied relativistic gas, whose particles practically do not interact with each other, but experience rare collisions with matter in the interstellar and interplanetary media and are exposed to cosmic magnetic fields. Cosmic ray particles have enormous kinetic energy (up to Ek of the order of 10 21 eV). Near the Earth, the overwhelming majority of cosmic rays are particles with energies from 10 6 eV to 10 9 eV; with a further increase in energy, the flux of cosmic rays sharply weakens. Thus, at an energy of 10 12 eV, no more than 1 particle/(m 2 ·s) falls on the atmospheric boundary, and at E k = 10 15 eV - only 1 particle/(m 2 ·year). This causes certain difficulties in studying cosmic rays of high and ultra-high energies. Although the total flux of cosmic rays near the Earth is small [only about 1 particle/(cm 2 s)], their energy density (about 1 eV/cm 3) within our Galaxy is comparable to the energy density of the total electromagnetic radiation of stars, the energy of interstellar thermal motion gas and the kinetic energy of its turbulent movements, as well as the energy density of the Galactic magnetic field. It follows that cosmic rays must play a large role in many astrophysical processes.

Another important feature of cosmic rays is the non-thermal origin of their energy. Indeed, even at a temperature of 10 9 K, apparently close to the maximum for stellar interiors, the average energy of thermal motion of particles is ≈ 3·10 5 eV. The majority of cosmic ray particles observed near the Earth have energies above 10 6 eV. This means that cosmic rays acquire energy through acceleration in specific astrophysical processes of plasma and electromagnetic nature.

According to their origin, cosmic rays can be divided into several groups:

1) cosmic rays of galactic origin (galactic cosmic rays, GCR); their source is our Galaxy, in which particles are accelerated to energies of about 10 18 eV;

2) cosmic rays of metagalactic origin; they are formed in other galaxies and have the highest, ultra-relativistic energies - over 10 18 eV;

3) solar cosmic rays (SCRs) generated on or near the Sun during solar flares and coronal mass ejections; their energy ranges from 10 6 to more than 10 10 eV;

4) anomalous cosmic rays (ACRs) formed in the Solar system at the periphery of the heliosphere; ACL particle energies are in the range of 1-100 MeV/nucleon.

Based on the content of Li, Be and B nuclei, which are formed as a result of interactions of GCRs with atoms of the interstellar medium, it is possible to determine the amount of matter X through which cosmic rays passed while wandering in the interstellar medium. The value of X is approximately equal to 5·10 g/cm2. The wandering time of cosmic rays in the interstellar medium (or their lifetime) and the value of X are related by the relation X ≈ ρνt, where ρ is the average density of the interstellar medium (about 10 -24 g/cm 3), t is the wandering time of cosmic rays in this medium, ν - particle speed. The value of ν for ultrarelativistic cosmic rays is practically equal to the speed of light, and their lifetime is about 3·10 8 years. (The lifetime of GCRs is determined by their exit from the Galaxy or absorption due to inelastic interactions with the matter of the interstellar medium.)

Entering the Earth's atmosphere, primary cosmic rays destroy the nuclei of the most common chemical elements in the atmosphere - N and O - and give rise to a cascade process in which all known elementary particles participate, in particular secondary particles such as protons (p), neutrons (n) , mesons (μ), electrons (e), as well as γ-quanta and neutrinos (ν). It is customary to characterize the path traveled by a particle of cosmic rays in the atmosphere before the collision by the amount of substance in grams contained in a column with a cross section of 1 cm 2, i.e., to express the path of particles in g/cm 2 of atmospheric substance. This means that after a beam of protons with an initial intensity I 0 passes through the thickness of the atmosphere x (g/cm 2), the number of protons that did not experience a collision will be equal to I = I 0 exp(-x/λ), where λ is the average path of the particle. For protons, which make up the bulk of primary cosmic rays, the range λ in air is approximately 70 g/cm 2 ; for He nuclei λ≈25 g/cm 2, for heavier nuclei - even less. Protons experience their first collision with atmospheric particles at an average altitude of 20 km (x≈70 g/cm2). The thickness of the atmosphere at sea level is equivalent to 10 30 g/cm 2, i.e. corresponds to approximately 15 nuclear ranges for protons. It follows that the probability of reaching the Earth's surface without experiencing collisions is negligible for a primary particle. Therefore, on the surface of the Earth, cosmic rays are detected only by weak ionization effects created by secondary particles.

Methods for studying cosmic rays. Since cosmic ray particles differ in energy by a factor of 10–15, to study them it is necessary to use very diverse methods and instruments. In this case, for example, equipment installed on satellites and space rockets is widely used. In the Earth's atmosphere, measurements are carried out using small balloons and large high-altitude balloons, on its surface - using ground-based installations. Some of them reach sizes of hundreds of square kilometers and are located either high in the mountains, or deep underground, or at great depths in the ocean, where secondary high-energy muons penetrate. Continuous recording of cosmic rays on the Earth's surface for more than 50 years has been carried out by a worldwide network of stations for studying cosmic ray variations - standard neutron monitors and muon telescopes. Valuable information about GCRs and SCRs is provided by observations at special installations such as the Baksan complex for studying extensive air showers (EAS).

The main types of detectors that are used in the study of cosmic rays are photographic emulsions and X-ray films, ionization chambers, gas-discharge counters, neutron counters, Cherenkov and scintillation counters, solid-state semiconductor detectors, spark and drift chambers.

Nuclear physics studies of cosmic rays are carried out mainly using large-area counters for recording EAS. Showers contain a huge number of secondary particles, which are formed during the invasion of one primary particle with an energy of over 10 15 eV. The main goal of such observations is to study the characteristics of an elementary act of nuclear interaction at high energies. Along with this, they provide information on the energy spectrum of cosmic rays at energies of 10 15 -10 20 eV, which is very important for searching for sources and mechanisms of cosmic ray acceleration.

The flux of particles with an energy of about 10 20 eV, studied by EAS methods, is very small. For example, per 1 m 2 at the boundary of the atmosphere, only one particle with Ε ≈ 10 19 eV falls per 1 million years. To register such small flows, it is necessary to have large areas covered by detectors. According to various estimates, giant installations for detecting EASs recorded from 10 to 20 events generated by particles with maximum energies of up to 3·10 20 eV.

Variations of cosmic rays with energies of the order of 10 9 -10 12 eV are studied using data from a worldwide network of neutron monitors, muon telescopes and other detectors. However, due to atmospheric absorption, ground-based installations are insensitive to particles with energies less than 500 MeV. Therefore, instruments for recording such particles are raised on sounding balloons into the stratosphere to altitudes of 30-35 km.

Extra-atmospheric measurements of the flux of cosmic rays with an energy of 1-500 MeV are carried out using geophysical rockets, satellites and space probes. Direct observations of cosmic rays in interplanetary space, begun in the 1960s in Earth orbit (near the ecliptic plane), have been carried out over the poles of the Sun since 1994 (Ulysses spacecraft). The space probes Voyager 1 and Voyager 2, launched in 1977, have already reached the limits of the solar system. Thus, the first of these spacecraft crossed the boundary of the heliosphere in 2004, the second - in 2007. Since 2008, both spacecraft have apparently been moving in a cloud of interstellar dust in which the Solar System is immersed.

A number of valuable results were obtained by the method of cosmogenic isotopes formed during the interaction of cosmic rays with meteorites and cosmic dust, with the surface of the Moon, planets, with the atmosphere or matter of the Earth. Cosmogenic isotopes carry information about past cosmic ray variations and solar-terrestrial connections. For example, using the content of 14 C radionuclide in tree rings, one can study variations in the intensity of cosmic rays over the past several thousand years. Using other long-lived nuclides (10 Be, 26 Al, 53 Mn, etc.) contained in meteorites, lunar soil, and deep-sea marine sediments, it is possible to reconstruct a picture of changes in the intensity of cosmic rays over millions of years.

With the development of space technology and radiochemical methods of analysis, it has become possible to study the characteristics of cosmic rays by their tracks (traces) in matter. Tracks are formed by cosmic ray nuclei in meteorites, lunar matter, in special target samples exposed on satellites and returned to Earth, etc. An indirect method is also used to study cosmic rays by the ionization effects they cause in the lower part of the ionosphere, especially in polar latitudes. These effects are significant mainly during the intrusion of SCRs into the atmosphere.

Origin of cosmic rays. Due to the high isotropy of cosmic rays, observations near the Earth do not allow us to determine where they are formed and how they are distributed in the Universe. Radio astronomy answered these questions for the first time in connection with the discovery of cosmic synchrotron radiation in the frequency range 10 7 -10 9 Hz. This radiation is created by electrons of very high energy (about 10 9 -10 10 eV) when they move in the magnetic fields of the Galaxy. Such electrons, which are one of the components of cosmic rays, occupy an extended region covering the entire Galaxy and is called the galactic halo. In interstellar magnetic fields, electrons move like other high-energy charged particles - protons and heavier nuclei. The only difference is that, due to their low mass, electrons, unlike heavier particles, intensively emit radio waves and thereby find themselves in distant parts of the Galaxy, being an indicator of cosmic rays.

In addition to the general galactic synchrotron radio emission, its discrete sources were discovered: supernova shells, the galactic core, radio galaxies, quasars, active galactic nuclei, etc. It is natural to assume that all these objects can be sources of cosmic rays. Supernova explosions are considered the main source of cosmic rays inside the Galaxy. Cosmic rays are accelerated by the shock waves generated by these explosions. The maximum energy that particles can acquire in such processes is about 10 16 eV. In addition, some cosmic rays can be accelerated to the same energies by shock waves propagating in the interstellar medium of the Galaxy. Cosmic rays of even higher energies are formed in the Metagalaxy; one of their sources may be the nuclei of active galaxies.

In 1966, K. Greisen (USA), as well as G. T. Zatsepin and V. A. Kuzmin (USSR), suggested that the spectrum of cosmic rays at energies above 3 10 19 eV should be “cut off” (bend sharply downward) from -due to the interaction of high-energy particles with cosmic microwave background radiation (the so-called GZK effect). The registration of several particles with an energy of the order of 10 20 eV can be explained if we assume that the sources of these particles are distant from us at a distance of no more than 50 Mpc. In this case, the interaction of cosmic rays with photons of the cosmic microwave background radiation practically does not occur due to the small number of photons on the path of the particle from the source to the observer. Data obtained in 2007 as part of the international Auger project seem to indicate for the first time the existence of the GZK effect at energies above 3·10 19 eV.

In the early 1970s, the study of low-energy GCRs carried out using spacecraft led to the discovery of an anomalous component of cosmic rays. It consists of incompletely ionized atoms of He, C, N, O, Ne and Ar. In the energy range from several units to several tens of MeV/nucleon, the spectrum of ACR particles differs significantly from the GCR spectrum: an increase in the particle flux is observed, which is believed to be associated with the acceleration of ions in the shock wave at the boundary of the heliomagnetosphere and the subsequent diffusion of these particles into the inner regions of the heliosphere. In addition, the prevalence of ACL elements differs significantly from the corresponding values ​​for GCR.

According to data as of June 2008 obtained from the Voyager 1 spacecraft, the flux of cosmic rays is constantly growing as they move away from the Solar System. This first information about cosmic rays directly from the interstellar medium raises new questions about the sources and nature (generation mechanisms) of the anomalous component of cosmic rays.

Mechanisms of cosmic ray acceleration. Supernova explosions are considered the main source of GCRs. The requirements for the energy power of sources generating cosmic rays are very high (the generating power of cosmic rays should be on the order of 3·10 33 W), so that ordinary stars in the Galaxy cannot satisfy them. However, such power can be obtained from supernova explosions (V.L. Ginzburg and S.I. Syrovatsky, 1963).

If during an explosion an energy of about 10 44 J is released, and explosions occur with a frequency of 1 time in 30-100 years, then their total power is about 10 35 W, and only a few percent of the energy of a supernova explosion is sufficient to provide the necessary power of cosmic rays.

The most likely mechanism for accelerating GCRs to energies of the order of 10 15 eV (and possibly higher) is the movement of the shell ejected during a supernova explosion, which generates a shock wave in the surrounding interstellar medium. The diffusion propagation of charged particles captured in the acceleration process allows them to repeatedly cross the front of the shock wave (G. F. Krymsky, 1977). Each pair of successive intersections increases the energy of the particle in proportion to the energy already achieved, which leads to the acceleration of the particles. With an increase in the number of intersections of the shock wave front, the probability of leaving the acceleration region also increases, so that as the energy increases, the number of particles decreases approximately according to a power law, and the acceleration turns out to be very effective, and the spectrum of accelerated particles is very hard (~ E -2). Under certain model assumptions, the proposed scheme gives a maximum energy value of the order of 10 17 Z eV, where Z is the charge of the accelerated nucleus.

Among other acceleration mechanisms, in particular, acceleration by a standing shock wave during the rotation of a neutron star with a powerful magnetic field (about 10 12 G) is discussed; the maximum particle energy in this case can reach (10 17 - 10 18) Z eV, and the effective acceleration time can be 10 years. Particle acceleration is also possible in shock waves during galactic collisions. Such an event can occur with a frequency of approximately 1 time in 5·10 8 years; the maximum achievable energy is estimated as 3·10 19 Z eV. The process of acceleration by shock waves in jets generated by active galactic nuclei leads to a similar assessment. The highest estimates (up to energies of the order of 10 21 eV) can be obtained within the framework of the model of the cosmological origin of gamma-ray bursts. Scenarios in which cosmic rays are formed as a result of decays or annihilation of so-called topological defects (cosmic string, monopoles, etc.) that arose in the first moments of the expansion of the Universe are also discussed.

Problems and prospects. The study of cosmic rays provides valuable information about electromagnetic fields in various regions of outer space. Information “recorded” and “transferred” by cosmic ray particles on their way to Earth is deciphered in the study of cosmic ray variations - spatiotemporal changes in the cosmic ray flux under the influence of dynamic, electromagnetic and plasma processes in interstellar space, inside the heliosphere (in the solar flux wind) and in the vicinity of the Earth (in the Earth's magnetosphere and atmosphere).

On the other hand, as a natural source of high-energy particles, cosmic rays play an indispensable role in studying the structure of matter and interactions between elementary particles. The energies of individual cosmic ray particles are so high that they will remain out of competition for a long time in comparison with particles accelerated by the most powerful laboratory accelerators.

Cosmic rays are important for studying the distant past of the Earth (climate changes, evolution of the biosphere, etc.), as well as for solving some practical problems (for example, monitoring and forecasting space weather, and ensuring radiation safety of astronauts).

At the end of the 20th and beginning of the 21st century, the possible role of cosmic rays in atmospheric and climate processes has attracted increasing attention. Although the energy density of cosmic rays is small compared to the energy of various atmospheric processes, cosmic rays appear to play a decisive role in some of them. In the earth's atmosphere at altitudes less than 30 km, cosmic rays are the main source of ion formation. The processes of condensation and the formation of water droplets largely depend on the ion density. Thus, during decreases in GCR intensity in the region of solar wind disturbances in interplanetary space caused by flares (the so-called Forbush effect), cloudiness and precipitation levels decrease. After solar flares and the arrival of SCRs on Earth, the amount of cloudiness and precipitation levels increase. These changes in both the first and second cases are at least 10%. After the invasion of the polar regions of the Earth by large flows of accelerated particles from the Sun, a change in the temperature of the upper layers of the atmosphere is observed. Cosmic rays are also actively involved in the formation of thunderstorm electricity. Currently, the influence of cosmic rays on ozone concentration and other processes in the atmosphere is being intensively studied.

All of these effects are studied in detail within the framework of the more general problem of solar-terrestrial connections. Of particular interest is the study of the mechanisms of these connections, in particular the trigger mechanism, in which an energetically weak primary impact on an unstable system leads to a multiple increase in secondary effects (for example, to the development of a powerful cyclone).

Lit.: Miroshnichenko L.I. Cosmic rays in interplanetary space. M., 1973; aka. Solar activity and the Earth. M., 1981; Dorman L.I. Experimental and theoretical foundations of cosmic ray astrophysics. M., 1975; Dorman I.V. Cosmic rays: Historical outline. M., 1981; she is the same. Cosmic rays, accelerators and new particles. M., 1989; Toptygin I. N. Cosmic rays in interplanetary magnetic fields. M., 1983; Murzin V.S. Introduction to cosmic ray physics. 3rd ed. M., 1988; Astrophysics of cosmic rays / Edited by V. L. Ginzburg. 2nd ed. M., 1990; Klapdor-Kleingrothaus G.V., Züber K. Astrophysics of elementary particles. M., 2000; Kapitonov I. M. Introduction to the physics of nuclei and particles. 3rd ed. M., 2006; Cherepashchuk A. M., Chernin A. D. Universe, life, black holes. Fryazino, 2007.

L. I. Miroshnichenko.

Cosmic rays

a flow of high-energy particles, mainly protons, coming to Earth from outer space (primary radiation), as well as secondary radiation generated by them in the Earth’s atmosphere as a result of interaction with atomic nuclei, in which almost all known elementary particles are found.

K. l. - a unique natural source of particles of high and ultra-high energies, which make it possible to study the processes of transformation of elementary particles and their structure. Along with this, K. l. make it possible to detect and study large-scale astrophysical processes associated with the acceleration and propagation of cosmic radiation particles in the interplanetary, interstellar, and possibly intergalactic medium.

Most particles of primary cosmic radiation have energies greater than 10 9 ev (1 Gav), and the energy of individual particles reaches 10 20 -10 21 ev(and maybe higher). Before the creation of powerful charged particle accelerators (See Charged particle accelerators) K. l. were the only source of high energy particles. In K. l. Many previously unknown elementary particles were discovered for the first time and the first data on their decays and interactions with atomic nuclei were obtained. Although modern accelerators (especially colliding beam accelerators) make it possible to conduct a thorough study of particle interaction processes up to energies of 10 11 -10 12 ev, K. l. are still the only source of information about particle interactions at even higher energies.

The overwhelming majority of primary K. l. comes to Earth from outside the Solar System - from the surrounding galactic space (Galaxy) , so-called galactic cosmic rays, and only a small part of them, mainly of moderate energies (GeV) , associated with the activity of the Sun, the so-called. solar K. l. However, during periods of high solar activity, short-term strong increases in solar radiation fluxes can occur. in interplanetary space. Particles of the highest energies (>10 17 ev) are possibly of extragalactic origin (come from the Metagalaxy (See Metagalaxy)).

The total flow of energy brought by K. l. to Earth (Cosmic rays0.01 erg by 1 cm 2 in 1 sec), is extremely small compared to the flux of solar energy emitted to the Earth and is comparable to the energy of visible radiation from stars. However, it is possible that in the distant past K. l. played a certain role in accelerating the evolution of life on Earth.

On the scale of the entire Galaxy, the average energy density of cosmic rays. great (Cosmic rays 1 eV/cm 3) - on the order of the densities of all other types of energy: gravitational energy (See Gravity) (gravity), magnetic fields, kinetic energy of the movement of interstellar gas, energy of electromagnetic radiation of stars. Therefore K. l. can have a noticeable impact on the evolution of the Galaxy as a whole.

In physics K. l. Two main areas of research are clearly distinguished: nuclear physical (the interaction of cosmic rays with matter; generation, properties, and interactions of elementary particles) and cosmophysical (composition and energy spectrum of primary cosmic rays; generation and propagation of solar and galactic cosmic rays). change in time of the intensity of cosmic rays and the interaction of cosmic rays with the Earth’s magnetosphere (See Magnetosphere of the Earth), with solar wind (See Solar wind) and shock waves in interplanetary space, etc.). With the development of accelerator technology, the field of research in the first direction is gradually shifting towards high energies. Increasingly in-depth study of near space by direct methods using satellites and space rockets moves the center of gravity of the second direction to more distant space objects. Therefore, scientific results obtained with the help of cosmic rays are, as a rule, of an exploratory, pioneering nature and are of fundamental importance both for the development of the physics of the microworld (in the region of characteristic sizes ≤10 -13 cm), and for the development of space physics (10 8 -10 28 cm).

Discovery and main stages of research on K. l. The existence of K. l. was established in 1912 by W. Hess based on the ionization of air molecules they produce; the increase in ionization with altitude proved their extraterrestrial origin. Observations of traces of cosmic particles. in a Wilson chamber (See Wilson chamber) , placed in the field of a laboratory magnet (D. V. Skobeltsyn , 1927), and their deflections in the Earth’s magnetic field using gas-discharge counters raised into the stratosphere (See Stratosphere) on cylinders (S.N. Vernov and R. Millikan, 1935-37), proved that primary cosmic rays. represent a stream of charged particles, mainly protons (nuclei of hydrogen atoms). At the same time, the energies of most of the cosmic rays were measured. (up to 15 Gav). Using nuclear photographic emulsions (See Nuclear photographic emulsion) , raised to a height of Cosmic rays 30 km(B. Peters et al., 1948), as part of primary K. l. traces of nuclei of elements heavier than hydrogen were discovered, up to iron nuclei ( rice. 1 ).

Detailed study of the charges and masses of particles of secondary cosmic rays. led to the discovery of many new elementary particles, in particular the positron a, muon (See Muons), pi-meson (See Pi-mesons), K-meson (See K-mesons) , Λ- hyperon (See Hyperons) (1932-49). In 1932, P. Blackett and J. Occhialini first discovered in a cloud chamber groups of genetically related particles of cosmic radiation with similar directions - the so-called. showers. In experiments 1945-49 at high-mountain stations of K. l. (V.I. Veksler , N.A. Dobrotin and others) and in the stratosphere (S.N. Vernov and others) it was established that secondary cosmic radiation is formed as a result of the interaction of primary cosmic rays. with the nuclei of air atoms. Later G. T. Zatsepin showed that the same mechanism, but at higher energies (≥10 14 ev) explains the development of previously discovered in K. l. (P. Auger , 1938) widespread air showers - flows of many millions of particles covering areas of the order of 1 at sea level km 2 and more.

For the correct approach to the problem of the origin of K. l. the successes of radio astronomy played a major role (See Radio astronomy). Related to K. l. non-thermal cosmic radio emission made it possible to detect their possible sources. In 1955, V. L. Ginzburg and I. S. Shklovsky, on the basis of radio-astronomical observations and energy estimates, for the first time quantitatively substantiated the hypothesis of supernovae (See Supernovae) as one of the main galactic sources of cosmic rays.

The basis for the cosmophysical direction of research was created in the 50-60s. an extensive worldwide network of KL stations. (over 150), which continuously record cosmic radiation. Many stations are located high in the mountains, at some stations underground observations are carried out, and cylinders with automatic registration devices for cosmic rays are regularly sent into the stratosphere.

New opportunities for direct study of primary K. l. in a very wide range of energies were discovered in connection with the rise of recording equipment on artificial Earth satellites and interplanetary automatic stations. In particular, using an ionization calorimeter (See ionization calorimeter) On the Proton series satellites, the energy spectrum of primary cosmic rays was directly measured for the first time. to energy Cosmic rays10 15 ev(Soviet physicist N.L. Grigorov and others, 1965-1969). Later, with the help of artificial satellites of the Moon and Mars, as well as on the Soviet Lunokhod-1 (1970-71), long-term measurements of variations in the composition and intensity of cosmic rays were carried out outside the Earth’s magnetosphere,

Primary galactic cosmic rays Geomagnetic effects. All experimental data agree with the fact that the flow of primary cosmic rays flying towards the Earth from the Galaxy is isotropic with a high degree of accuracy (Cosmic rays 0.1%), that is, does not depend on direction. Getting into the Earth's magnetic field, charged particles of cosmic radiation deviate from their original direction (as a result of the action of the Lorentz force on them (See Lorentz force)). Therefore, the intensity of K. l. and their energy spectrum in near-Earth space depend both on the geomagnetic coordinates of the observation site and on the direction of arrival of the cosmic rays. The deflecting effect of the geomagnetic field is stronger, the larger the angle ϑ between the direction of particle motion and the direction of the field line, i.e., the smaller the geomagnetic latitude φ observation places. Thus, for the same particle energy, the deviation is maximum in equatorial regions and minimum near the magnetic poles. At the equator, this “geomagnetic barrier” does not allow protons with energies less than cosmic rays flying perpendicular to its surface to reach the Earth15 Gav and nuclei with energy Cosmic rays 7.5 Gav per nucleon (proton or neutron). With increasing geomagnetic latitude, the threshold particle energy decreases rapidly ( Cosmic rayscos 4 φ), and in the polar regions there is practically no geomagnetic barrier. Along with the regular latitude dependence on the intensity of cosmic rays. geomagnetic field anomalies have a noticeable effect (especially in the South Atlantic region). As a result, the intensity distribution of cosmic rays. across the globe has a rather complex character ( rice. 2 ). In the polar regions (φ≥ 60°), the intensity of cosmic rays. at the boundary of the atmosphere is about 0.4 particles per 1 cm 2 in 1 sec per unit of solid angle.

With increasing energy K. l. their intensity first slowly, and then more and more sharply decreases ( rice. 3 , A). At energies 10 10 -10 15 ev flow of particles with energy above some given energy E(integral spectrum) falls according to the law Cosmic rays E -1.7 (rice. 3 , b). In the energy region > 10 15 ev the only source of information about the energy spectrum of cosmic rays. ( rice. 3 , f) are data on extensive air showers (see below): this spectrum can no longer be represented by a single power law, which can be explained by the admixture of metagalactic cosmic rays.

More than 90% of particles of primary K. l. of all energies are protons, approximately 7% - α -particles and only a small fraction (Cosmic rays 1%) falls on the nuclei of elements heavier than hydrogen and helium. Despite this, kernels with Z> 1 carry about 50% of the total energy of cosmic rays. A decrease in prevalence with an increase in the atomic number of an element in cosmic rays. goes slower than for the matter of celestial bodies in the Universe in general. Especially great in K. l. the content of nuclei of light elements Li, Be, B, the natural abundance of which is extremely low (≤ 10 -7%). There is also an excess of heavy nuclei ( Z≥ 6). It follows from this that in the sources of K. l. acceleration of heavy nuclei predominates, and lighter nuclei arise due to the splitting of heavy nuclei (fragmentation) during their interaction with interstellar matter. In the period 1966-71, with the help of nuclear photographic emulsions and solid-state detectors of charged particles in cosmic rays. nuclei significantly heavier than iron have been discovered - up to uranium, and possibly even heavier, and their fluxes decrease with increasing Z something like Z -7 - Z -8 . In the most studied energy region (>2.5 Gav per nucleon) nuclear composition of cosmic l. is as follows: protons - about 92%, α-particles - about 7%, nuclei with Z = 3-5 - about 0.1-0.15%, s Z= 6-9 - about 0.5% s Z= 10-15 - about 0.1-0.15%, s Z= 16-25 - about 0.04%, s Z = 26 (iron) - 0.025%, s Z> 30- Cosmic rays10 -5%.

According to the content in K. l. Li, Be, and B, which are not present in the sources (these elements quickly burn up as a result of thermonuclear reactions occurring in stars) and which are formed only as a result of fragmentation, the average amount of matter through which cosmic rays pass was estimated. on the way from the sources to the Earth; it turned out to be equal to 3-5 g/cm2. From here, if the average density of matter in the Galaxy is known, it is possible to estimate the path traversed by cosmic rays. in the Galaxy, and the average lifetime of cosmic rays. (see below).

The composition of primary K. l. also includes electrons and positrons (Cosmic rays1%) and high-energy photons - γ -quanta (Cosmic rays 0.01% at energies > 100 Mev). Despite the insignificant share in K. l., γ -quanta are of particular interest because, without being deflected by the magnetic fields of interstellar space, they make it possible to detect individual quasi-point sources of cosmic rays. About 20 such sources have already been found. Of these, the most interesting is the pulsar (See Pulsars) NP 0532 in the Crab Nebula, which produces a stream γ -quanta 0.1-0.5 per 1 m 2 in 1 sec and at the same time being a powerful pulsating source of X-ray radiation. In addition, a diffuse flux of -λ quanta from the center of the Galaxy was discovered with an intensity of Cosmic rays of 1 particle per 1 m 2 in 1 sec per unit solid angle.

Inside the Earth's magnetosphere, at altitudes ≥ 1000 km From the earth's surface, in addition to the cosmic ray flux, there are much more intense fluxes of protons and electrons, captured by the geomagnetic field and forming the Earth's radiation belt (See Earth's radiation belts). The origin of the inner region of the radiation belt is explained mainly by the reverse flow (albedo) of neutrons knocked out by cosmic rays. from the nuclei of atoms that make up the Earth's atmosphere: neutrons decay into protons and electrons, which are held in the natural magnetic trap (See Magnetic traps) of the Earth's magnetosphere.

Solar K. l. The strongest increases in the intensity of cosmic rays. in the form of irregular short-term bursts are associated with chromospheric flares (See Chromospheric flares) on the Sun. With such flares, charged particles accelerate. solar plasma (See Plasma) by electromagnetic fields (apparently at the boundaries of sunspots), that is, the generation of solar cosmic rays. In particular, a very probable mechanism for the acceleration of particles by electric fields induced during the rapid approach of regions of solar plasma with oppositely directed magnetic fields has been proposed (Soviet physicist S.I. Syrovatsky, 1965).

Fluxes of solar radiation During some chromospheric flares, fluxes of galactic cosmic rays are hundreds of times higher. Thus, with a record surge on February 23, 1956, a 300-fold increase in the cosmic ray flux was observed. with energy > 3 Gav, which could pose a serious threat to the safety of space flights. Therefore, systematic observations of chromospheric flares, bursts of radio and X-ray radiation, and other manifestations of solar activity are very important, which make it possible, in close connection with measurements of the intensity of cosmic rays. predict the radiation situation on space flight routes.

On average, the contribution of solar cosmic rays The total intensity of cosmic radiation is several percent.

Chemical composition of solar cells. very close to the composition of the solar atmosphere. Unlike galactic Cosmic rays do not contain Li, Be, or B nuclei. This shows that the amount of matter passed through solar cosmic rays is extremely small (g/cm2) and that their generation cannot occur in the depths of the solar atmosphere, where the density of the substance is too high (most likely acceleration occurs in the upper chromosphere and lower corona of the Sun).

Particles of solar cosmic l. Compared to galactic ones, they have lower energies (their energy spectrum is softer). Proton energies are usually limited to fractions Gav, and only during very rare powerful chromospheric flares are protons generated with energies up to 100 Gav; lower limit on the energy of recorded solar electrons. is tens kev(i.e. close to the energy of solar wind particles). Solar K. l. low energies have a significant impact on the state of the ionosphere (See Ionosphere) of the Earth at high latitudes, causing additional ionization of its lower layers. This leads to a weakening of radio waves, and in some cases to a complete cessation of short-wave radio communications. Data on the distribution of solar cosmic rays, their energy spectrum, and angular anisotropy make it possible to obtain information about the structure of the magnetic field in interplanetary space. Study of spatial and temporal variations (changes) in the fluxes of solar cosmic rays. helps to better understand geophysical phenomena such as geomagnetic storms, auroras, etc.

The nature of the increase in the flux of solar radiation. to Earth shows that in the initial period after the flare the flow is significantly anisotropic, with its maximum directed at an angle of approximately 45° west of the direction to the Sun. This was the first direct evidence of the curvature of the interplanetary magnetic field lines in the form of Archimedean spirals (see Fig. rice. 4 ).

Modulation of galactic cosmic rays solar wind. Among the periodic time variations in the intensity of galactic. K. l. the main role is played by intensity modulations that coincide with the 11-year cycle of solar activity. These modulations are associated with the scattering and “sweeping out” of cosmic rays. of galactic origin by non-uniformly magnetized regular streams of plasma ejected from the Sun at speeds of 300-500 km/sec. Such streams, called solar wind, extend far beyond the Earth’s orbit [by tens of astronomical units (See Astronomical unit) (AU); 1 a. e. ≈ 150 million km], gradually turning into turbulent plasma motion in the layer bordering the undisturbed galactic magnetic field ( rice. 4 ). According to data on the last two cycles (1948-59 and 1959-70), the intensity of K. l. near the boundary of the earth's atmosphere during maximum solar activity decreases by 2-2.5 times compared to the value characteristic of the minimum. At sea level, where low-energy particles do not reach, the amplitude of 11-year variations in cosmic rays. turns out to be much smaller ( rice. 5 ).

There are other, less pronounced types of galactic modulations. K. l., due to various reasons. These are, in particular, 27-day variations associated with the period of rotation of the Sun around its axis, as well as solar-diurnal variations associated with the rotation of the Earth and the anisotropy of the electromagnetic properties of the medium in which cosmic rays propagate. The totality of information about modulation effects leads most researchers to the conclusion that the effective dimensions of the modulation region of cosmic rays are solar wind is 2-5 a. e.

Origin and age of galactic cosmos. The main source of K. l. Supernova explosions are considered. With each such explosion, the shell of the star expands at a tremendous speed and shock waves arise in the plasma, leading to the acceleration of charged particles to energies of Cosmic rays 10 15 ev and higher. The main experimental argument in favor of the hypothesis of the origin of cosmos l. From supernova explosions, for the first time, direct radio astronomy observation of partially polarized radio emission from the Crab Nebula (1957), which arose as a result of an explosion in supernova 1054, relatively close to the Solar System. The properties of this radiation are such that it should be attributed to synchrotron radiation (See Synchrotron radiation) (magnetobremsstrahlung) - the radiation of fast electrons in magnetic fields, “frozen” into the streams of stellar plasma ejected during the explosion of this supernova. Later, it was possible to observe magnetic bremsstrahlung radio emission from other, more distant nebulae generated by supernova explosions. Further observations showed that the spectrum of magnetic bremsstrahlung of electrons extends to the optical, x-ray and even γ ranges, and this is associated with very high electron energies (up to Cosmic rays 10 12 ev). Naturally, along with electrons in the expanding shells of supernovae, intense acceleration also occurs of heavy charged particles - protons and nuclei (however, due to their large mass, they do not experience noticeable energy losses due to radiation in magnetic fields). Moreover, the heavier the nucleus, the more favorable the initial conditions of acceleration (the so-called injection) can be: heavy nuclei can be in an incompletely ionized state and therefore deflect relatively weakly in magnetic fields, which facilitates their “leakage” beyond the dense shell of the star ( in which the magnetic field is high). If we take into account the average frequency of supernova explosions in the Galaxy in general (once every 30-50 years) and the total energy release in each explosion (10 51 -10 52 erg, or 10 63 -10 64 ev) and assume that cosmic rays 1% of this energy is spent on accelerating charged particles, then can be explained as the average energy density of cosmic rays. (Cosmic Rays 1 eV/cm 3), and the absence of noticeable fluctuations in the flow of cosmic l.

Even more powerful sources of cosmic rays have been detected using radio astronomy methods. (more precisely, their electronic components), located far beyond the boundaries of our Galaxy. Such sources are, in particular, intensely emitting quasi-stellar objects of short extent - Quasars, the nuclei of some galaxies (See Galaxies) , experiencing a sharp expansion of an explosive type, as well as Radio galaxies with their characteristic powerful ejections of matter (accompanied by radio emission on the scale of entire galaxies).

Heavy charged particles accelerated in galactic sources then spread along complex trajectories in interstellar space, where they are influenced by weak [(3-6)10 -6 gs] irregular and inhomogeneous magnetic fields of interstellar plasma clouds. Charged particles become “entangled” in these magnetic fields (the strength of which increases significantly in the regions of the spiral arms of the Galaxy, simultaneously with an increase in the concentration of interstellar plasma). At the same time, the movement of K. l. has the nature of diffusion, in which particles with energies up to 10 17 -10 18 ev can be held within our Galaxy for tens of millions of years. Diffusion movement of particles of cosmic l. causes almost complete isotropy of their flow. Only at higher energies do the radii of curvature of particle trajectories (especially protons) become comparable to the size of galaxies and an intense “leakage” of cosmic rays occurs. into metagalactic space. Despite the high degree of rarefaction of matter, long-term travel of particles in the Metagalaxy leads to energy losses in new processes - photonuclear reactions on background electromagnetic radiation (it is called relict radiation (see Relict radiation)) , left over from the early stages of expansion of the once hot Universe. The presence of this process greatly reduces the likelihood that the most energetic part of the spectrum of cosmic rays. due to the metagalactic component.

Fundamentally new possibilities for experimental study of the sources of the most energetic part of the spectrum of cosmic rays. (up to energies 10 20 -10 21 ev) were discovered after the discovery of unique astrophysical objects - pulsars. According to modern concepts, pulsars are small (Cosmic rays 10 km in diameter) neutron stars that arose as a result of rapid gravitational compression (gravitational collapse (See gravitational collapse)) of unstable stars such as supernovae. Gravitational collapse leads to a colossal increase in the density of the star’s matter (up to nuclear density and higher), magnetic field (up to 10 13 gs) and rotation speed (up to 10 3 revolutions per sec). All this creates favorable conditions for the acceleration of heavy charged particles to exceptionally high energies Cosmic rays 10 21 ev and electrons to energies Cosmic rays 10 12 ev. Indeed, observations have shown that, along with radio emission, pulsars emit (with the same period) light, X-rays, and sometimes γ- radiation that can only be explained by the process of magnetic bremsstrahlung radiation of very fast electrons. Thus, synchrotron radiation of cosmic ray electrons, caused by strong magnetic fields localized near unstable “hot” objects - cosmic ray sources, makes it possible to solve the problem of the origin of cosmic rays. methods of observational astronomy (radio astronomy, X-ray astronomy (See X-ray astronomy), gamma astronomy (See Gamma astronomy)).

Important additional information about the sources and age of K. l. provide studies of the nuclear composition of K. l. From the small relative content in K. l. Be nuclei it follows that the radioactive isotope 10Be (the average lifetime of which is about 2 million years) manages to decay almost completely, which gives an estimate of the upper limit of the age of cosmic rays. 20-50 million years. Estimates of approximately the same order (10-30 million years) are obtained from the relative content of the group of light nuclei (Li, Be, B) as a whole, as well as from the average time required for cosmic ray electrons. for diffuse propagation from intragalactic sources to the boundaries of the Galaxy. Analysis of the composition of the superheavy nuclear component ( Z> 70) gives the average age of K. l. no more than 10 million years.

Another way to test various hypotheses of the origin of K. l. - measurement of K. l intensity. in the distant past, in particular during periods of known outbursts of nearby supernovae (for example, outbursts in 1054). There are two methods by which the effects of increasing cosmic radiation intensity could be detected. in the past, not only as a result of the explosion of supernovae relatively close to the Solar System, but also as a result of possible much more powerful explosive processes in the core of the Galaxy. This is the radiocarbon method, in which the concentration of the 14 C isotope in various tree rings of very old trees determines the rate of accumulation in the atmosphere of 14 C, formed as a result of nuclear reactions under the influence of radiation, and the meteorite method, based on the study of the composition of stable and radioactive isotopes meteorite matter exposed to prolonged exposure to cosmic rays. These methods indicate that the average intensity of cosmic rays. differed relatively little from modern times for tens of thousands and billions of years, respectively. Constancy of intensity of K. l. over a billion years makes the hypothesis about the origin of all cosmic rays unlikely. during the explosion of the core of our Galaxy, which is considered responsible for the formation of the galactic halo (not yet proven by direct observations).

Interaction of K. l. with substance.

1. Nuclear active component K-l. and multiple particle generation. During the interaction of protons and other nuclei of primary cosmic rays. high energy (Cosmic rays are several Gav and above) with the nuclei of atoms of the earth’s atmosphere (mainly nitrogen and oxygen), the nuclei split and the birth of several unstable elementary particles occurs (the so-called multiple processes) , mainly π-mesons (pions) - charged (π +, π -) and neutral (π 0) with lifetimes of 2.5․10 -8 sec and 0.8․10 -16 sec respectively. With a much lower probability (5-10 times) K-mesons are born, and with an even lower probability - hyperons and almost instantly decaying resonances. On rice. 6 a photograph of multiple particle production recorded in a nuclear photographic emulsion is shown; particles fly out from one point in the form of a narrow beam. The average number of secondary particles formed in one interaction of a proton (or π-meson) with a light nucleus or one nucleon of such a nucleus increases with increasing energy E first according to a power law close to E 1/3(up to E≈ 20 Gav), and then (in the energy region 2․10 10 -10 13 ev) this growth slows down and is better described by a logarithmic dependence. At the same time, indirect data on widespread air showers indicate processes of significantly higher multiplicity at energies ≥ 10 14 ev.

The angular direction of the flow of born particles in a wide range of energies of the primary and born particles is such that the momentum component perpendicular to the direction of the primary particle (the so-called transverse momentum) averages 300-400 MeV/s, Where With - speed of light in vacuum (at very high energies E particles when the rest energy of the particle mc2 can be neglected in comparison with its kinetic energy, the momentum of the particle R = E/c; Therefore, in high energy physics, momentum is usually measured in units MeV/s).

During a collision, primary protons lose on average about 50% of their initial energy (at the same time, they can experience charge exchange, turning into neutrons).

Secondary nucleons (protons and neutrons) formed during the splitting of nuclei and high-energy charged pions generated in collisions will also (together with the primary protons that have lost some of their energy) participate in nuclear interactions and cause the splitting of the nuclei of air atoms and the multiple formation of pions. The average distance over which one nuclear interaction occurs is usually measured by the specific mass of the material traveled; for primary protons, cosmic rays are 90 g/cm 2 air, i.e. Cosmic rays 9% of the entire thickness of the atmosphere. As the atomic weight of a substance increases A the average mileage gradually increases (approximately as A 1/3), reaching Cosmic Rays 160 g/cm 2 for lead. The birth of pions occurs mainly at high altitudes (20-30 km), but continues to a lesser extent throughout the entire thickness of the atmosphere and even at a depth of several m soil.

The nucleons of nuclei emitted during nuclear collisions and charged high-energy pions that do not have time to decay form the nuclear-active component of secondary cosmic rays. Repeated repetition of successive, cascade interactions of nucleons and charged pions with the nuclei of air atoms, accompanied by multiple generation of new particles (pions) in each act of interaction, leads to an avalanche-like increase in the number of secondary nuclear-active particles and to a rapid decrease in their average energy. When the energy of an individual particle becomes less than 1 Gav, the birth of new particles practically stops and only processes of partial (and sometimes complete) splitting of the atomic nucleus with the emission of nucleons of relatively low energies remain (as a rule). The total flux of particles of the nuclear-active component decreases as they penetrate deeper into the atmosphere ( rice. 7 , curve 1), and at sea level (Cosmic rays 1000 g/cm 2) less than 1% of nuclear-active particles remain.

2. Electron-photon showers and the soft component of secondary K. l. Neutral pions formed during interactions of particles of a nuclear-active component with atomic nuclei almost instantly decay (due to their very short lifetime) into two photons ( γ ) each: π°→2 γ . This process gives rise to the electron-photon component of cosmic rays. (it is also called soft, i.e. easily absorbed, component).

In strong electric fields of atomic nuclei, these photons give rise to electron-positron pairs e - e + ( γ →e - +e +), and electrons and positrons, in turn, through bremsstrahlung (See Bremsstrahlung) emit new photons (e ± →e ± + γ ) etc. Such processes, which are of a cascade nature, lead to an avalanche-like increase in the total number of particles - to the formation of an electron-photon shower. The development of an electron-photon shower leads to a rapid fragmentation of the energy π 0 into an increasing number of particles, i.e., to a rapid decrease in the average energy of each particle of the shower. After the maximum development of the soft component, achieved at a height of about 15 km(Cosmic rays 120 g/cm 2), its gradual attenuation occurs ( rice. 7 , curve 2). When the energy of each particle becomes less than a certain critical value (for air the critical energy is about 100 Mev), the predominant role begins to be played by energy losses due to ionization (See Ionization) of air atoms and Compton scattering (See Compton effect); the increase in the number of particles in the shower stops, and its individual particles are quickly absorbed. Almost complete absorption of the electron-photon component occurs at relatively small thicknesses of matter (especially high density); in laboratory conditions, it is enough to have a lead screen with a thickness of 10-20 cm(depending on particle energy). The electron-photon shower recorded in a cloud chamber is shown in rice. 8.

The main characteristic of an electron-photon shower is a change in the number of particles with increasing thickness of the material passed through - the so-called. cascade curve ( rice. 9 ). According to the theory of this process, the number of particles at the maximum of the cascade curve is approximately proportional to the energy of the original particle. The angles of deviation of particles from the shower axis are determined by the scattering of electrons and positrons, and the average transverse momentum is about 20 Mev/s.

Along with π° mesons in cosmic l. There are other sources of formation of electron-photon showers. These are electrons and γ -high energy quanta (> 100 Mev) primary K. l., as well as δ -electrons, that is, atomic electrons knocked out due to the direct electrical interaction of fast charged particles of cosmic rays passing through matter.

At very high energies (≥ 10 14 ev) electron-photon showers in the earth's atmosphere acquire the specific features of widespread atmospheric showers. In such showers, a very large number of successive multiplication cascades leads to a strong increase in the total flux of particles (calculated depending on the energy in many millions and even billions) and to their wide spatial divergence - by tens and hundreds m from the axis of the shower. In widespread air showers near the Earth's surface, one shower particle falls on approximately several (2- 3 )Gav energy of the primary particle that caused the shower. This makes it possible to estimate, based on the total flux of particles in a shower, the energy of the “ancestors” of these showers arriving at the boundary of the earth’s atmosphere, which cannot be done directly due to the extremely low probability of them directly hitting the observation point.

Due to the high density of particle flux in a wide atmospheric shower, relatively intense directed electromagnetic radiation is emitted both in the optical region of the spectrum and in the radio range. The optical part of the glow is determined by the Cherenkov-Vavilov radiation process (See Cherenkov-Vavilov radiation) , since the speeds of most particles exceed the phase speed of light in air. The mechanism of radio emission is more complex; it is connected, in particular, with the fact that the Earth’s magnetic field causes a spatial separation of flows of negatively and positively charged particles, which is equivalent to the emergence of a time-varying electric current. dipole (See Dipole).

3. Cosmic muons and neutrinos. Penetrating component of secondary radiation. Arising in the atmosphere under the influence of cosmic rays. charged pions participate in the development of the nuclear cascade only at sufficiently high energies - until their decay in flight begins to affect them. In the upper layers of the atmosphere, decay processes become significant already at energies ≤ 10 12 ev.

Charged peony (with energy ≤ 10 11 ev) decays into a muon μ ± (charged unstable particle with rest mass m μ ≈207 me, Where me - electron mass, and average lifetime τ 0 ≈ 2․10 -6 sec) and neutrinos ν (neutral particle with zero rest mass). In turn, the muon decays into a positron (or electron), a neutrino, and an antineutrino. Because the speeds of muons (like all other cosmic ray particles) are very close to the speed of light With, then, in accordance with the theory of relativity, the average time before their decay τ quite large - proportional to the total energy E, τ = Electromagnetic interactions)) and lose their energy mainly to the ionization of atoms (Cosmic rays 2 Mev at thickness 1 g/cm 2). Therefore, the muon flux is the penetrating component of cosmic rays. Even with relatively moderate energy Cosmic rays 10 Gav A muon can not only pass through the entire earth's atmosphere (see. rice. 7 , curve 3) , but also to penetrate deep into the Earth at distances of about 20 m soil ( rice. 10 ). The maximum depth at which the highest energy muons were recorded is about 8600 m translated into water equivalent. Due to their great penetrating ability, it is muons that form the “skeleton” of widespread air showers over large (hundreds of m) distances from their axis.

Thus, simultaneously with the development of the nuclear cascade described above, it is “overgrown” with an electron-photon component (due to the decay of π 0), as well as (due to the decays of π + and π -) - penetrating muon component ( rice. eleven ).

High penetrating ability combined with an absorption coefficient directly proportional to the density of the substance at moderate energies (tens and hundreds Gav) makes the penetrating component of K. l. a very convenient tool for underground geophysical and engineering exploration ( rice. 12 ). Measuring the intensity of K. l. using a counter telescope (See Counter telescope) in the adits and comparing the data obtained with known absorption curves of cosmic rays. in water or soil, you can detect or clarify the positions of ore layers and voids, as well as measure the weight load on the soil from structures standing on it.

At energies of the order of 10 12 ev and higher, along with ionization losses of muon energy, energy losses for the formation of electron-positron pairs and bremsstrahlung, as well as for direct interactions with the atomic nuclei of matter, become increasingly significant. As a result, at depths ≥ 8 km water equivalent at angles ≥ 50° to the vertical, the flux of cosmic muons turns out to be negligible. Experiments carried out since 1964 in the mines of India and South Africa with installations of enormous area made it possible to detect at these depths at angles > 50° an additional flux of muons, the only source of which could only be the interactions of neutrinos with the atomic nuclei of matter. These experiments presented a unique opportunity to study the properties of the most penetrating - neutrino - component of cosmic rays. The most important problem in this case is the study of the interaction of ultra-high-energy neutrinos with matter; in particular, to elucidate the structure of elementary particles, it is of particular interest to study the increase in the cross section of interaction (decrease in the “transparency” of matter) with increasing neutrino energy. Such an increase in the neutrino interaction cross section has been established at accelerators up to energies of 10 10 ev. It is very important to investigate whether this increase in the cross section will continue up to energies of 10 15 ev(corresponding to the characteristic distance of weak interactions 6․10 -17 cm).

Problems and prospects. Further study of K. l. in laboratories and space stations continues in two directions. In the cosmophysical direction, the nature of those basic processes in which acceleration of particles to high and ultra-high energies can occur (in supernovae, pulsars, and partly on the Sun) is being clarified, as well as the properties of the interplanetary and interstellar medium based on variations in the intensity of cosmic rays and the characteristics of their composition , angular and energy distribution. Especially great hopes are placed on research in the field of X-ray and gamma-ray astronomy in close connection with radio astronomy and astronomical observations of possible sources of cosmic rays.

Also interesting is the question of the role of neutrinos as one of the components of primary cosmic rays. at energies ≥ 10 20 ev. The occurrence of extensive atmospheric showers of such high energies is already difficult to explain by charged particles accelerated within our Galaxy, and particles of intergalactic origin cannot gain such energies due to collisions with photons of the cosmic microwave background radiation filling the Metagalaxy. Therefore, we have to take into account the possibility of a continuous increase in the opacity of matter (in particular, atmospheric air) for cosmic neutrino flows, which in this case could become the “ancestors” of the most powerful widespread showers.

Attempts are being made to finally solve the still unclear problem of the existence of fireballs - hypothetical particles (with cosmic ray masses 3-5 Gav, and sometimes much higher), almost instantly decaying after their birth into individual particles (mainly pions) according to the laws of statistical physics. Discussions about the degree of applicability of describing the multiple production of particles using models of hydrodynamic and thermodynamic types, in which highly excited “hadronic matter” with an indefinite number of particles formed during nuclear collisions expands until it disintegrates into individual free particles, are far from over.

Lit.: Ginzburg V.L., Syrovatsky S.I., Origin of cosmic rays, M., 1963; Dorman L.I., Variations of cosmic rays and space exploration, M.. 1963; Dorman L.I., Miroshnichenko L.I., Solar cosmic rays, M., 1968; Dorman L.I., Smirnov V.S., Tyasto M.I., Cosmic rays in the Earth’s magnetic field, M., 1971; Murzin V.S., Sarycheva L.I., Cosmic rays and their interaction, M., 1968; Bugaev E.V., Kotov Yu.D., Rosenthal I.L., Cosmic muons and neutrinos, M., 1970; Bondarenko V.M., The use of cosmic rays in geology, M., 1965. Popular lit.: Rossi B., Cosmic rays, trans. from English, M., 1966; Dobrotin N. A., Cosmic Rays, M., 1963; Zhdanov G. B., High energy particles, M., 1965; Ginzburg V.L., Origin of cosmic rays, M., 1968.

Cosmic rays are streams of fast charged particles - protons, electrons, nuclei of various chemical elements, flying in various directions in outer space at a speed of more than 100,000 km/s. Entering the earth's atmosphere, cosmic ray particles collide with the nuclei of nitrogen and oxygen atoms and destroy them. As a result, streams of new elementary particles arise. Such particles born in the atmosphere are called secondary cosmic rays. Secondary cosmic rays are recorded by special devices - ionizing particle counters or using special nuclear photographic emulsions. Primary cosmic rays practically do not reach the Earth, and only a small amount of them is registered high in the mountains. Research on these particles is carried out mainly outside the Earth's atmosphere using modern space technology.

The bulk of cosmic rays arriving at the Earth have an energy of more than eV (1 eV is equal to J). For comparison, we point out that in the interior of the Sun, where matter is heated to a temperature of 15,000,000 K, the average energy of plasma particles is only slightly higher than 103 eV, i.e., it is many times less than that of cosmic rays.

Cosmic rays penetrate literally every square centimeter of interplanetary and interstellar space every second. An area with a surface area of ​​1 m2 receives an average of about 10,000 particles per second. These are mainly particles of relatively low energies. The higher the energy of cosmic particles, the less common they are. Thus, particles with very high energy exceeding eV fall on an area of ​​1 m2 on average once a year.

Particles with fantastic energy in eV are extremely rare. Where they were able to obtain such great energy remains unknown.

More than 90% of primary cosmic rays of all energies are protons, about 7% are from -particles (the nuclei of helium atoms), about 2% are from the nuclei of atoms heavier than helium, and about 1% are from electrons.

By their nature, cosmic rays are divided into solar and galactic.

Solar cosmic rays have relatively low energy and are formed mainly during solar flares (see Solar activity). The acceleration of particles of these cosmic rays occurs in the chromosphere and corona of the Sun. Streams of solar cosmic rays after particularly strong solar flares can pose a serious radiation hazard to astronauts.

Primary cosmic rays coming from outside into the Solar System are called galactic. They move in interstellar space along rather intricate trajectories, constantly changing their flight direction under the influence of the magnetic field that exists between the stars of our Galaxy.

Drawing (see original)

The electrons that make up cosmic rays are gradually slowed down in the magnetic field, losing energy to emit radio waves. This type of radiation is called synchrotron radiation. It is recorded by radio telescopes. By observing it, it is possible to identify areas of increased concentration of cosmic rays. It turned out that cosmic rays are concentrated mainly in the disk of our Galaxy, several thousand light years thick (near the plane of the Milky Way). The total energy of all cosmic rays in this layer is measured by a giant figure - J.

The main source of cosmic rays in interstellar space is apparently supernova explosions. It is no coincidence that supernova remnants emit powerful synchrotron radiation. Rapidly rotating magnetized neutron stars also contribute. They are capable of imparting high energies to charged particles. Very powerful sources of cosmic rays can be active galactic nuclei, as well as radio galaxies with their characteristic ejections of matter, accompanied by very powerful radio emission.

Having received great energy, cosmic ray particles wander around the Galaxy in various directions for tens of millions of years before losing their energy in collisions with atoms of rarefied interstellar gas.

The study of cosmic rays is one of the most fascinating branches of astrophysics. Observations of cosmic rays (direct registration of them, analysis of synchrotron radiation or the effects of their interaction with the environment) allow us to better understand the mechanisms of energy release during various cosmic processes and to clarify the physical properties of the interstellar medium under the continuous influence of cosmic rays. Observations are also important for studying the physics of those elementary particles that arise during the interaction of cosmic rays with matter. A significant contribution to this branch of physics was research carried out using spacecraft, including those launched in the 60s. in the USSR four heavy Proton satellites.