Cosmic rays

The differential energy spectrum of cosmic rays has a power-law character (on a logarithmic scale, an inclined straight line) (minimum energies — yellow zone, solar modulation; average energies — blue zone, GCR; maximum energies — purple zone, extragalactic CL)

Cosmic rays are elementary particles and nuclei of atoms moving with high energies in space ^[1] ^[2] .

Basic Information

The physics of cosmic rays is considered to be part of high energy physics and elementary particle physics .

The physics of cosmic rays is studying:

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

The study of fluxes of high-energy charged and neutral cosmic particles that fall on the boundary of the Earth’s atmosphere is the most important experimental problem.

Classification by origin of cosmic rays:

outside of our galaxy;
in the galaxy;
in the sun;
in interplanetary space.

Primary called extragalactic, galactic and solar cosmic rays.

Secondary cosmic rays are called streams of particles arising under the action of primary cosmic rays in the Earth's atmosphere and recorded on the surface of the Earth.

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

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

The energy spectrum of cosmic rays by 43% consists of the energy of protons , another 23% - of the energy of helium nuclei (alpha particles) and 34% of the energy transferred by other particles ^[3] .

By the number of particles, cosmic rays are 92% composed of protons, 6% are helium nuclei, about 1% are heavier elements, and about 1% are electrons ^[3] ^[4] . When studying sources of cosmic rays outside the Solar System, the proton-nuclear component is mainly detected by the orbital gamma telescopes generated by the gamma-ray flux , and the electronic component by the synchrotron radiation generated by it (in particular, by the meter waves). radiation in the interstellar medium field), and in case of strong magnetic fields in the region of the cosmic ray source, also to higher frequency ranges. Therefore, the electronic component can also be detected by ground-based astronomical instruments ^[5] ^[1] .

Traditionally, particles observed in CR are divided into the following groups: p $(Z=1),$ ${\ displaystyle (Z = 1),}$ α $(Z=2),$ ${\ displaystyle (Z = 2),}$ L $(Z=3...5),$ ${\ displaystyle (Z = 3 ... 5),}$ M $(Z=6...9),$ ${\ displaystyle (Z = 6 ... 9),}$ H $(Z\geqslant 10),$ ${\ displaystyle (Z \ geqslant 10),}$ VH $(Z\geqslant 20)$ ${\ displaystyle (Z \ geqslant 20)}$ (respectively, protons, alpha particles, light, medium, heavy and super heavy). The peculiarity of the chemical composition of primary cosmic radiation is the abnormally high (several thousand times) content of the nuclei of group L ( lithium , beryllium , boron ) compared with the composition of stars and interstellar gas ^[3] . 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 ^[4] . This assumption is confirmed by the fact that CRs have a very high degree of isotropy .

History of cosmic ray physics

For the first time, an indication of the possibility of the existence of ionizing radiation of extraterrestrial origin was obtained at the beginning of the 20th century in experiments on the study of the conductivity of gases. The detected spontaneous electric current in the gas could not be explained by the ionization arising from the natural radioactivity of the Earth. The observed radiation was so penetrating that in the ionization chambers shielded by thick layers of lead, a residual current was still observed. In the years 1911-1912, a series of experiments with ionization chambers on balloons was carried out. Hess discovered that radiation increases with altitude, while ionization caused by Earth’s radioactivity would have to fall with altitude. In the experiments of Kolkherster , it was proved that this radiation is directed from top to bottom.

In 1921-1925, the American physicist Milliken , studying the absorption of cosmic radiation in the atmosphere of the Earth depending on the height of observation, found that in lead this radiation is absorbed in the same way as the gamma radiation of nuclei. Milliken was the first to call this radiation cosmic rays.

In 1925, Soviet physicists L. A. Tuvim and L. V. Mysovsky made measurements of the absorption of cosmic radiation in water: it turned out that this radiation was absorbed ten times weaker than the gamma radiation of nuclei. Mysovsky and Tuwim also found that the radiation intensity depends on the barometric pressure - they discovered the "barometric effect". The experiments of D. V. Skobeltsyn with a Wilson camera placed in a constant magnetic field made it possible to “see,” due to ionization, the traces (tracks) of cosmic particles. DV Skobeltsyn discovered cosmic particle showers.

Experiments in cosmic rays made it possible to make a number of fundamental discoveries for the physics of the microworld.

In 1932, Anderson discovered a positron in cosmic rays. In 1937, Muders were discovered by Anderson and Neddermeyer and the type of their decay was indicated. In 1947, π- mesons were discovered. In 1955, cosmic rays established the presence of K-mesons , as well as heavy neutral particles - hyperons .

The quantum characteristic " oddity " appeared in experiments with cosmic rays. Experiments in cosmic rays raised the question of parity preservation, discovered the processes of multiple generation of particles in nucleon interactions, and made it possible to determine the effective cross section for the interaction of high-energy nucleons.

The appearance of space rockets and satellites led to new discoveries — the discovery of the Earth’s radiation belts (February 1958, Van Allen and, independently of it, July of the same year, S. N. Vernov and A. E. Chudakov ^[6] ), and allowed to create new methods for the study of galactic and intergalactic spaces.

Flows of high-energy charged particles in near-earth space

In near-Earth space, several types of cosmic rays are distinguished. Galactic cosmic rays (GCR), albedo particles, and the radiation belt are usually considered stationary. To non-stationary - solar cosmic rays (SCR).

Galactic Cosmic Rays (GCR)

Galactic cosmic rays (GCR) consist of the nuclei of various chemical elements with a kinetic energy E of more than several tens of MeV / nucleon , as well as electrons and positrons with E > 10 MeV . These particles come into interplanetary space from the interstellar medium. The most probable sources of cosmic rays are flashes of supernovae and the resulting pulsars. Electromagnetic fields of pulsars accelerate charged particles, which are then scattered in interstellar magnetic fields ^[7] . It is possible, however, that in the region E <100 MeV / nucleon particles are formed due to the acceleration in the interplanetary medium of particles of the solar wind and interstellar gas. The differential energy spectrum of the GCR has a power character.

Secondary particles in the Earth’s magnetosphere: radiation belt , albedo particles

Inside the magnetosphere , as in any dipole magnetic field , there are areas that are inaccessible for particles with a kinetic energy E less critical. The same particles with energy E < E _cr , which are still there already, cannot leave these areas. These forbidden areas of the magnetosphere are called capture zones. In the zones of capture of the dipole (quasi-dipole) field of the Earth, significant flows of trapped particles (primarily, protons and electrons) are indeed retained.

In near-Earth space, two toroid-shaped regions can be distinguished, located in the equatorial plane approximately at a distance of 300 km (in the BMA zone) to 6,000 km (internal RPG) and from 12,000 km to 40,000 km (external RPG). The main filling of the inner belt are protons with high energies from 1 to 1000 MeV , and the outer one - electrons.

The maximum intensity of low-energy protons is located at distances L ~ 3 of the Earth's radii from its center. Low-energy electrons fill the entire capture region. For them, there is no separation between the inner and outer belts. The proton flux in the inner belt is fairly stable over time.

The process of interaction of the nuclei of primary cosmic radiation with the atmosphere is accompanied by the appearance of neutrons . The neutron flux from the Earth ( albedo neutrons) freely passes through the Earth’s magnetic field . Since neutrons are unstable (the average decay time is ~ 900 s ), some of them decay in areas inaccessible to charged particles of low energy. Thus, the decay products of neutrons (protons and electrons) are born directly in the capture zones. Depending on the energy and pitch angles, these protons and electrons can either be trapped or leave this region.

Albedo particles are secondary particles reflected from the Earth’s atmosphere . The albedo neutrons provide the radiation belt with protons with energies up to 10³ M eV and electrons with energies up to several MeV.

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. In the lower part of this range, SCRs are adjacent to the protons of high-speed solar wind streams. SCR particles appear due to solar flares .

Ultrahigh-energy cosmic rays

The energy of some particles (for example, Oh-My-God particles ) exceeds the limit of the GZK (Greisen - Zatsepin - Kuzmina) - the theoretical limit of energy for cosmic rays 5 1910 ¹⁹ eV , caused by their interaction with photons of background radiation . Several dozen such particles were registered by the AGASA Observatory . These observations do not yet have a sufficiently substantiated scientific explanation.

Registration of cosmic rays

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

Modern observatories work on other principles. When a high-energy particle enters the atmosphere, it interacts with the air atoms in the first 100 g / cm² and creates a whole squall of particles, mainly pions and muons , which, in turn, give rise to other particles, and so on. A cone of particles is formed, which is called a shower. Such particles move with a speed exceeding the speed of light in the air, due to which the Cerenkov glow appears, which is detected by telescopes. This technique allows you to monitor areas of the sky in the area of hundreds of square kilometers.

Value for space flight

The visual phenomenon of cosmic rays

The cosmonauts of the ISS , when they close their eyes, no more than once every 3 minutes, see flashes of light ^[8] , perhaps this phenomenon is due to the action of high-energy particles entering the retina of the eye. However, this is not experimentally confirmed, it is possible that this effect has a purely psychological basis.

Radiation

Prolonged 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 United States are already looking for ways to solve this problem.

Notes

↑ ¹ ² Miroshnichenko L. I. Cosmic rays // Physical encyclopedia : [in 5 tons.] / Ch. ed. A. M. Prokhorov . - M .: Soviet Encyclopedia, 1990. - T. 2: Quality factor - Magnetooptics. - p. 471-474. - 704 s. - 100 000 copies - ISBN 5-85270-061-4 .
↑ Cosmic radiation. Tutorial.
↑ ¹ ² ³ V. L. Ginzburg and S. I. Syrovatsky. Current status of the question of the origin of cosmic rays . UFN . - 1960. - V. 71 , no. 7 - p . 411-469 .
↑ ¹ ² Dorman, 1975 , p. 18.
↑ V. L. Ginzburg . Cosmic Rays: 75 Years of Research and Future Prospects // Earth and Universe . - M .: Science , 1988. - № 3 . - p . 3-9 .
↑ Scientific discoveries of Russia.
↑ Shirkov, 1980 , p. 236.
↑ Roscosmos. Maxim Suraev's blog.

Literature

Murzin SV Physics of cosmic rays. - M .: Publishing House of Moscow State University . - 1970.
Murzin SV Introduction to the physics of cosmic rays. - M .: Atomizdat . - 1979.
Model of outer space. - M .: Publishing House of Moscow State University , in 3 volumes.
A. D. Filonenko. Radio astronomy method of measuring ultrahigh-energy cosmic particle fluxes (rus.) // UFN . - 2012. - T. 182 . - p . 793-827 .
Dorman L.I. Experimental and theoretical foundations of astrophysics of cosmic rays. - M .: Science, 1975. - 464 p.
ed. Shirkov D.V. Physics of the microworld. - M .: Soviet Encyclopedia, 1980. - 528 p.
Panasyuk M. I. The Wanderers of the Universe or the Big Bang Echo. - M .: Century 2, 2005. - 272 p. - ISBN 5-85099-160-3 .

Links

[ФЭ2-1] ¹ ² Miroshnichenko L. I. Cosmic rays // Physical encyclopedia : [in 5 tons.] / Ch. ed. A. M. Prokhorov . - M .: Soviet Encyclopedia, 1990. - T. 2: Quality factor - Magnetooptics. - p. 471-474. - 704 s. - 100 000 copies - ISBN 5-85270-061-4 .

[2] Cosmic radiation. Tutorial.

[Ginz-3] ¹ ² ³ V. L. Ginzburg and S. I. Syrovatsky. Current status of the question of the origin of cosmic rays . UFN . - 1960. - V. 71 , no. 7 - p . 411-469 .

[_1ca2a0b52d10b1e0-4] ¹ ² Dorman, 1975 , p. 18.

[ZiV0388-5] V. L. Ginzburg . Cosmic Rays: 75 Years of Research and Future Prospects // Earth and Universe . - M .: Science , 1988. - № 3 . - p . 3-9 .

[6] Scientific discoveries of Russia.

[_579c0a28a1cd0991-7] Shirkov, 1980 , p. 236.

[8] Roscosmos. Maxim Suraev's blog.