What are cosmic rays. Cosmic rays (Cosmic radiation)

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Cosmic rays - elementary particles and nuclei of atoms moving at high energies in outer space.

Basic information

Physics of cosmic rays 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;
• particles of cosmic rays, their nature and properties;
• phenomena caused by particles of cosmic rays in outer space, the atmosphere of the Earth and planets.

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

Classification according to the origin of cosmic rays:

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

Primary called 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% of the energy of protons, another 23% of the energy of helium (alpha particles) and 34% of the energy carried by the rest of the particles.

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

Traditionally, the particles observed in CRs are divided into 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). feature chemical composition primary cosmic radiation is an anomalously high (several thousand times) content of nuclei of the L group (lithium, beryllium, boron) in comparison with 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 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 observed 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 in the ionization chambers, shielded by thick layers of lead, a residual current was still observed. In 1911-1912, a number of experiments were carried out with ionization chambers on balloons. Hess found that the radiation increases with height, while the ionization caused by the Earth's radioactivity would have to fall with height. In Kolcherster's experiments, it was 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 height of observation, found that in lead this radiation is absorbed in the same way as the gamma radiation of 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 weaker 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". Experiments by D. V. Skobeltsyn with a cloud chamber placed in a constant magnetic field made it possible to “see”, due to ionization, traces (tracks) of cosmic particles. DV 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. In the lower part of this range, SCRs border on the protons of high-speed solar wind streams. SCR particles appear due to solar flares.

Ultra-high energy cosmic rays

The energy of some particles exceeds the GZK limit (Greisen - Zatsepin - Kuzmin) - the theoretical energy limit for cosmic rays 5·10 19 eV, caused by their interaction with photons of cosmic microwave background radiation. Several dozen such particles were registered by the AGASA observatory per year. (English)Russian. 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 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 make observations is limited by its size.

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

Significance for space travel

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 of the eye. However, this has not been experimentally confirmed; it is possible that this effect has an exclusively psychological basis.

Prolonged exposure to cosmic radiation can have a very negative impact on human health. For the further expansion of mankind to other planets of the solar system, it is necessary to develop reliable protection against such dangers - 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. - S. 471-474. - 703 p. - ISBN 5852700614.
3. Ginzburg V.L. , Syrovatsky S.I. Current state the question of the origin of cosmic rays // UFN . - 1960. - No. 7.- S. 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 future prospects // Earth and Universe. - M .: Nauka, 1988. - No. 3. - pp. 3-9.
7. , With. 236.

Literature

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

Links

Components Nebulae Regions of star formation Circumstellar formations Radiation

An excerpt characterizing cosmic rays

At this time, Petya, whom no one paid any attention to, went up to his father and, all red, in a breaking voice, now rough, now thin, said:
“Well, now, papa, I will say decisively - and mother too, as you wish, - 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 heaven in horror, clasped her hands and angrily turned to her husband.
- That's the deal! - she said.
But the count recovered from his excitement at the same moment.
“Well, well,” he said. "Here's another warrior!" Leave the nonsense: you need to study.
“It’s not nonsense, daddy. Obolensky Fedya is younger than me and also goes, and most importantly, anyway, I can’t learn anything now, when ... - Petya stopped, blushed to a sweat and said the same: - when the fatherland is in danger.
- Full, full, 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 younger son.
- I'm telling you. So Pyotr Kirillovich will say ...
- I'm telling you - it's nonsense, the milk has not dried up yet, but he wants to serve in the military! Well, well, I'm telling you, - and the count, taking the papers with him, probably to read it again in the study before resting, left the room.
- Pyotr Kirillovich, well, let's go for a smoke ...
Pierre was confused and indecisive. Natasha's unusually brilliant and lively eyes incessantly, more than affectionately addressed to him, brought him to this state.
- No, I think I'm going home ...
- Like home, but you wanted to have an evening with us ... And then they rarely began to visit. And this one is mine ... - the count said good-naturedly, pointing to Natasha, - it’s only cheerful with you ...
“Yes, I forgot ... I definitely need to go home ... Things ...” Pierre said hastily.
“Well, goodbye,” said the count, leaving the room completely.
- Why are you leaving? Why are you upset? Why? .. - Natasha asked Pierre, defiantly looking into his eyes.
“Because I love you! he wanted to say, but he did not say it, blushed to tears and lowered his eyes.
“Because it’s better for me to visit you less often ... Because ... no, I just have business to do.”
- From what? no, tell me, - Natasha began decisively and suddenly fell silent. They both looked at each other in fear and embarrassment. He tried to smile, but could not: his smile expressed suffering, and he silently kissed her hand and went out.
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. Everyone did as if they had not noticed anything when he came to tea silent and gloomy, with tearful eyes.
The next day the Emperor arrived. Several of the Rostovs' servants asked to go and see the tsar. That morning, Petya spent a long time dressing, combing his hair and arranging 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, wants to serve the fatherland, that youth cannot be an obstacle to devotion and that he is ready ... Petya, while he was getting ready, prepared many beautiful 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 surprised everyone would be at his youth), and at the same time, in the arrangement of his collars, in his hairstyle and in a sedate, slow gait, he wanted to present himself as an old man. But the farther he went, the more he entertained himself with the people arriving and arriving at the Kremlin, the more he forgot to observe the degree and slowness characteristic of adults. Approaching the Kremlin, he already began to take care that he was not pushed, and resolutely, with a menacing look, put his elbows on his sides. But at the Trinity Gate, in spite of all his determination, people who probably did not know for what patriotic purpose he was going to the Kremlin pressed him against the wall so that he had to submit and stop while the carriages drove through the gate with a sound buzzing under the arches. Near Petya stood a woman with a footman, two merchants and a retired soldier. After standing for some time at the gate, Petya, without waiting for all the carriages to pass, wanted to move on before the others and began to work decisively with his elbows; but the woman standing opposite him, on whom he first directed his elbows, angrily shouted at him:
- What, barchuk, pushing, you see - everyone is standing. Why climb then!
“That’s how everyone will climb,” said the footman, and, also beginning to work with his elbows, squeezed Petya into the stinking corner of the gate.
Petya wiped away the sweat that covered his face with his hands and straightened his collars, soaked with sweat, which he arranged as well as the big ones at home.
Petya felt that he had an unpresentable appearance, and was afraid that if he presented himself to the chamberlains like that, he would not be allowed to see the sovereign. But there was no way to recover and go to another place because of the tightness. One of the passing generals was an acquaintance of the Rostovs. Petya wanted to ask for his help, but considered that it would be contrary to courage. When all the carriages had passed, the crowd poured in and carried Petya out to the square, which was all 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 on the square, he clearly heard the sounds of bells and joyful folk talk that filled the entire Kremlin.
At one time it was more spacious on the square, but suddenly all the heads opened, everything rushed somewhere forward. Petya was squeezed so that he could not breathe, and everyone shouted: “Hurrah! hooray! hurrah! Petya stood on tiptoe, pushed, pinched, but could see nothing but the people around him.
On all faces there was one common expression of tenderness and delight. One merchant's wife, who was standing near Petya, was sobbing, and tears flowed from her eyes.
- Father, angel, father! she said, wiping her tears with her finger.
- Hooray! shouted from all sides. For a minute the crowd stood in one place; but then she rushed forward again.
Petya, beside himself, clenching his teeth and savagely rolling his eyes, rushed forward, working with his elbows and shouting "Hurrah!"
"So that's what a sovereign is! thought Petya. – No, I can’t apply to him myself, it’s too bold! but at that moment the crowd staggered back (from the front the policemen were pushing those who had advanced 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 ribs in the side and was so crushed that suddenly everything became dim in his eyes and he lost consciousness. When he came to, some kind of clergyman, with a tuft of graying hair behind him, in a shabby blue cassock, probably a sexton, held him under the arm with one hand, and guarded him from the oncoming crowd with the other.
- Barchonka crushed! - said the deacon. - Well, so! .. easier ... crushed, crushed!
The sovereign went to the Assumption Cathedral. The crowd leveled off again, and the deacon led Petya, pale and not breathing, to the Tsar Cannon. Several people took pity on Petya, and suddenly the whole crowd turned to him, and there was already a stampede around him. Those who stood closer served him, unbuttoned his frock coat, seated cannons on a dais and reproached someone - those who crushed him.
- That way you can crush to death. What is this! Murder to do! Look, my heart, it has become white as a tablecloth, - said the voices.
Petya soon came to his senses, the color returned to his face, the pain disappeared, and for this temporary inconvenience he received a place on the cannon, with which he hoped to see the sovereign who was due to go back. Petya no longer thought about filing a petition. If only he could see him - and then he would consider himself happy!
During the service in the Assumption Cathedral - a united prayer service on the occasion of the arrival of the sovereign and thanksgiving prayer for the conclusion of peace with the Turks - the crowd spread; sellers of kvass, gingerbread, poppy seeds, which Petya was especially fond of, appeared shouting, and ordinary conversations were heard. One merchant's wife showed her torn shawl and reported how expensive it was bought; another said that nowadays all silk fabrics have become expensive. The sexton, Petya's savior, was talking to the official about who and who is serving with the bishop today. The sexton repeated the word soborne several times, which Petya did not understand. Two young tradesmen were joking with yard girls gnawing nuts. All these conversations, especially jokes with girls, which for Petya at his age had a special attraction, all these conversations now did not interest Petya; ou sat on his cannon dais, still agitated at the thought of the sovereign and of his love for him. The coincidence of the feeling of pain and fear, when he was squeezed, with the feeling of delight, further strengthened in him the consciousness of the importance of this moment.
Suddenly, cannon shots were heard from the embankment (these were fired in commemoration of peace with the Turks), and the crowd quickly rushed to the embankment - to watch how they were shooting. Petya also wanted to run there, but the deacon, who took the barchon under his protection, did not let him go. Shots were still going on when officers, generals, chamberlains ran out of the Assumption Cathedral, then others came out more slowly, their hats were again taken off their heads, and those who had run away to look at the guns ran back. Finally, four more men in uniforms and ribbons came out of the doors of the cathedral. "Hooray! Hooray! the crowd shouted again.
- Which? Which? Petya asked around him in a weeping voice, but no one answered him; everyone was too enthusiastic, and Petya, having chosen one of these four faces, whom he could not clearly see because of the tears that came out of joy in his eyes, focused all his delight on him, although it was not the sovereign, shouted “Hurrah! in a frantic voice and decided that tomorrow, no matter what it costs him, he will be a military man.
The crowd ran after the sovereign, escorted him to the palace and began to disperse. It was already late, and Petya hadn't eaten anything, and the sweat was pouring down from him; but he did not go home, and together with the diminished, but still quite large crowd, stood in front of the palace, during the emperor’s dinner, looking into the windows of the palace, expecting something else and equally envious of the dignitaries who drove up to the porch - for the emperor’s dinner, and the chamber lackeys who served at the table and flickered in the windows.
At dinner, the sovereign Valuev said, looking out the window:
“The people still hope to see Your Majesty.
Dinner was already over, the emperor 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, wept with happiness. A rather large piece of biscuit, which the sovereign held in his hand, broke off and fell on the railing of the balcony, from the railing to the ground. The coachman in the coat, who was standing nearest, 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 to him and began to throw biscuits from the balcony. Petya's eyes were filled with blood, the danger of being crushed excited him even more, he threw himself on the biscuits. He did not know why, but it was necessary to take one biscuit from the hands of the king, and it was necessary not to succumb. He rushed and knocked down an old woman who was catching a biscuit. But the old woman did not consider herself defeated, although she lay on the ground (the old woman caught biscuits and did not hit with her hands). Petya knocked her hand away with his knee, grabbed the biscuit and, as if afraid of being late, again shouted "Hurrah!", in a hoarse voice.
The sovereign left, and after that most of the people began to disperse.
“So I said that we still have to wait - and it happened,” the people said joyfully from different sides.
Happy as Petya was, he was still sad to go home and know that all the enjoyment 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 entered the regiment. Returning home, he resolutely and firmly announced that if they did not let him in, he would run away. And the next day, although not yet completely surrendered, Count Ilya Andreich went to find out how to put Petya somewhere safer.

On the morning of the 15th, on the third day after that, an innumerable number of carriages stood at the Sloboda Palace.
The halls were full. In the first there were nobles in uniforms, in the second, merchants with medals, in beards and blue caftans. There was a buzz and movement in the hall of the Nobility Assembly. At one large table, under the portrait of the sovereign, the most important nobles were sitting on chairs with high backs; but most of the nobles walked about the hall.
All the nobles, the very ones whom Pierre saw every day either in the club or in their homes, were all in uniforms, some in Catherine’s, some in Pavlov’s, some in new Alexander’s, some in the general noble one, and this general character of the uniform gave something strange and fantastic to these old and young, the most diverse and familiar faces. Especially striking were the old people, blind, toothless, bald, swollen with yellow fat or shriveled, thin. For the most part they sat in their places and were silent, and if they walked and talked, they would attach themselves to someone younger. Just as on the faces of the crowd that Petya saw on the square, on all these faces there was a striking feature of the opposite: a common expectation of something solemn and ordinary, yesterday - the Boston party, Petrushka the cook, the health of Zinaida Dmitrievna, etc.
Pierre, from early morning pulled together in an awkward, narrow noble uniform that had become him, was in the halls. He was in a state of agitation: the extraordinary assembly not only of the nobility, but also of the merchants - the estates, etats generaux - evoked in him a whole series of thoughts long abandoned, but deeply embedded 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 for a conference with his people, confirmed him in this look. And he, believing that in this sense something important was approaching, something that he had been waiting for a long time, he walked, looked closely, listened to the conversation, but nowhere did he find an expression of those thoughts that occupied him.

Cosmic rays are streams of high-energy charged particles that consist of protons. They come to Earth from all directions of interstellar space, including from the Sun. After occurring on , the intensity of the flows increases sharply. Cosmic rays resemble a very rarefied gas, in which the particles almost do not interact with each other. But, flying through the substance, they collide with the nuclei of its atoms and give rise to unstable elementary particles (they are detected by these traces). Near-Earth outer space is penetrated by cosmic rays of two types: stationary and non-stationary. The stationary ones include particle fluxes from , the non-stationary ones are the rays of solar origin.

Every second streams of all kinds of particles fall on the Earth from the depths of space. Cosmic rays overcome gigantic distances, but do not lose their power. They invade the atmosphere of our planet, ionizing its constituent gases. The pioneer of this discovery was W. Hess: with the help of hot air balloon he was able to determine that the ionization of gases does not decrease with height, as was thought, but increases. This indicated that the radioactive substance responsible for this process is not in our planet.

Kinds

Galactic

The energies of primary cosmic rays, which are atomic nuclei and elementary particles, are colossal and reach hundreds of GeV. As they pass through the earth's atmosphere, they create new particles called secondary cosmic rays. Cosmic rays travel huge distances within our galaxy, constantly changing directions. They have almost the speed of light, and the reason for the change in direction lies in the magnetic field. It is very difficult for rays to leave the galaxy, because its magnetic field is closed. This made it possible to confirm the theory that a magnetic field exists in our galaxy, to calculate its strength. From the calculations, it turns out that cosmic rays travel distances up to 10 27 cm over periods of billions of years. Based on the time of existence of particles, it is possible to determine the power of their sources. Such sources, for example, are. Cosmic rays are capable of heating rarefied gases to millions of degrees. A similar process exists, for example, in the convective zone of the Sun. These gases form a huge halo called the galactic corona.

Albedo

Some of the rays are reflected by the earth's atmosphere, creating secondary particles - albedo. Albedo neutrons supply the radiation belt with protons with energies up to 10 3 MeV and electrons with energies of several MeV.

solar

During solar flares, streams of charged particles are emitted. They are accelerated in the upper layers of the luminary's atmosphere and acquire sufficiently high energies. Registering them with earth's surface, against the background of higher-energy galactic streams, occurs in the form of a sharp increase in the intensity of the cosmic ray flux. The bulk of the sun's rays are protons with energies of 10 6 eV, and the upper limit of their energy is 2 . 10 10 eV.

ultra-high energy beams

The energy of the particles of such beams is higher than the admissible theoretical energy limit, which is 5 . 10 19 eV. This limit is due to their interaction with photons of the primary, relic, radiation. It turns out that these cosmic rays are wanderers from the depths of the Universe. The AGASA observatory tracked several dozen sources of ultra-high energy particles throughout the year.

Registration of cosmic rays

In modern observatories, tracking of traces of cosmic rays is carried out using telescopes. High-energy particles entering the atmosphere interact with air atoms. As a result, streams of pions and muons are born, which themselves form other particles. The process continues further, until the formation of a cone of particles, called a shower. Such particles have a speed that is higher than light (in air), so they glow. The method makes it possible to track areas of the sky hundreds of km2.

COSMIC RAYS, streams of high-energy charged particles that come to the Earth from all sides from outer space and constantly bombard its atmosphere. Cosmic rays are dominated by protons, there are also electrons, nuclei of helium and heavier chemical elements(up to nuclei with charge Z ≈ 30). The nuclei of hydrogen and helium atoms are the most numerous in cosmic rays (≈85 and ≈10%, respectively). The share of other nuclei is small (does not exceed ≈5%). A small part of cosmic rays are electrons and positrons (less than 1%). Cosmic radiation incident on the boundary earth's atmosphere, includes all stable charged particles and nuclei with lifetimes of the order of 106 years or more. In essence, only particles accelerated in distant astrophysical sources can be called truly "primary" cosmic rays, and "secondary" - particles formed in the process of interaction of primary cosmic rays with interstellar gas. Thus, electrons, protons and nuclei of helium, 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 partly, if not completely, secondary, but that fraction of them, which may have a primary origin, is now the subject of research.

History of cosmic ray research

In the beginning. 20th century in experiments with electroscopes and ionization chambers a permanent residual ionization of gases caused by some kind of penetrating radiation was discovered. In contrast to the radiation of radioactive substances environment, penetrating radiation could not stop even 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, the ionization caused by penetrating radiation increases. Its extraterrestrial origin was finally proved by R. Milliken in 1923-26 in experiments on the absorption of radiation by the atmosphere (it was he who introduced the term "cosmic rays").

The nature of cosmic rays until 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 with the help of telescopes, counters, Wilson chambers 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 geo magnetic field on the intensity and direction of arrival of primary cosmic rays showed that the vast majority of cosmic ray particles have a positive charge. Related to this is 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 determine the nuclear composition of primary cosmic rays (1948): traces of nuclei of heavy chemical elements, up to iron, were found. Primary electrons in cosmic rays were first registered only in 1961 in stratospheric measurements.

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

Characteristics and classification of cosmic rays

Cosmic rays resemble a highly rarefied relativistic gas, whose particles practically do not interact with each other, but experience rare collisions with the matter of 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 is made up of particles with energies from 10 6 eV to 10 9 eV, after which the cosmic ray flux sharply weakens. So, 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 the study of cosmic rays of high and ultrahigh (extreme) energies. Although the total flux of cosmic rays near the Earth is small (only approx. 1 particle / (cm 2 ∙ s)), their energy density (approx. 1 eV / cm 3) within our Galaxy is comparable to the energy density of the total electromagnetic radiation of stars, energy thermal motion interstellar gas and the kinetic energy of its turbulent motions, as well as with the energy density of the magnetic field of the Galaxy. Hence it follows that cosmic rays must play an important role in many astrophysical processes.

Other important feature cosmic rays - 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 the thermal motion of particles is ≈3∙10 5 eV. The main number of cosmic ray particles observed near the Earth has the energy of St. 10 8 eV. This means that cosmic rays acquire energy by accelerating 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 largest, ultrarelativistic energies (over 10 18 eV); 3) solar cosmic rays; generated at or near the Sun during solar flares And coronal mass ejections; their energy ranges from 10 6 eV to St. 10 10 eV; 4) anomalous cosmic rays; formed in 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 have passed while wandering in the interstellar medium. The X value 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≈ ρvt , where ρ is the average density of the interstellar medium, which is ~10 – 24 g/cm 3 , t is the wandering time of cosmic rays in this medium, v is the velocity of particles. It is usually assumed that the value of v for ultrarelativistic cosmic rays is practically equal to the speed of light c, so that their lifetime is approx. 3 10 8 years. It is determined either by the escape 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 such secondary particles as protons, neutrons, mesons, electrons, as well as γ-quanta and neutrinos. It is customary to characterize the path traveled by a cosmic ray particle in the atmosphere before the collision by the amount of matter in grams enclosed in a column with a cross section of 1 cm 2, i.e., to express the range of particles in g/cm 2 of atmospheric matter. This means that after passing through the atmosphere x (g/cm 2) by a proton beam with initial intensity I 0, the number of protons that did not experience collisions 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/cm2, 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 Earth's surface, cosmic rays are detected only by the weak effects of ionization created by secondary particles.

Cosmic rays near the earth

Cosmic rays of galactic and metagalactic origin occupy a huge energy range covering about 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, however, the characteristic value of their energy usually does not exceed 10 9 eV. Therefore, the division of cosmic rays into galactic and solar 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 solar activity(more precisely, from the interplanetary magnetic field changing during the solar cycles). In the region of higher energies, the intensity of galactic cosmic rays is practically constant in time. According to modern concepts, galactic cosmic rays proper terminate in the energy region between 10 17 and 10 18 eV. The origin of cosmic rays of extremely high energies, most likely, is not connected with the Galaxy.

There are four ways to describe the spectra of various components of cosmic rays. 1. The number of particles per unit of hardness. The propagation (and probably also the 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. The number of particles per unit of 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 gas. 3. The 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 of energy per nucleon, almost irrespective of whether the nucleons incident on the atmosphere are free protons or are bound in nuclei. 4. The number of particles per unit of energy per nucleus. Experiments on extensive air showers, which use the atmosphere as a calorimeter, generally measure a quantity that is related to the total energy per particle. The units for measuring the differential intensity of particles I are (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 range 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 the slope of approx. 3 10 15 eV (kink, sometimes called "knee", 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 abundance of various nuclei in galactic and solar cosmic rays, on the Sun and other stars (the content of oxygen nuclei is assumed 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
4Be - 5B	0,02	<10 – 5	<10 – 5	0,8
6C	0,54 *	0,60	0,26	1,8
7 N	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
14Si	0,13 *	0,065	0,045	0,12
15 P - 21 Sc	0,06	0,032	0,024	0,13
16 S - 20 Ca	0,04 *	0,028	0,02	0,11
22Ti - 28Ni	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 rest of the 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 index. OK. 79% of primary nucleons are free protons, approx. 70% of the remaining particles are nucleons bound in helium nuclei. Fractions (shares) of primary nuclei are almost constant in the indicated energy range (possibly with slight variations). On 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 value of J (E ) is the number of particles having energy in the range from E to E + δE and passing through a unit surface per unit time per unit solid angle in the 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 solar minimum 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
H	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 data on the intensity of particles of galactic cosmic rays of higher energies (≈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 assumed 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 the particles of cosmic rays differ by a factor of 10 15 in their energies, very diverse methods and instruments have to be used to study them (Fig. 3, left). In this case, the equipment installed on satellites and space rockets is widely used. In the Earth's atmosphere, measurements are carried out with the help of small balloons and large high-altitude balloons, on its surface - with the help of ground-based installations. Some of them reach hundreds of square kilometers in size 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). For more than 60 years, continuous recording of cosmic rays on the Earth's surface has been carried out by a worldwide network of stations for studying cosmic ray variations - standard neutron monitors and muon telescopes. Valuable information about galactic and solar cosmic rays is provided by observations on large facilities such as the Baksan complex for studying extensive air showers .

At present, the main types of detectors 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-physical studies of cosmic rays are carried out mainly with the help of large-area counters for recording extensive air showers, discovered in 1938 (P. Auger). Showers contain a huge amount of secondary particles, which are formed during the invasion of one primary particle with an energy of ≥ 10 15 eV. The main purpose 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 the search for sources and mechanisms of cosmic ray acceleration.

The flux of particles with E ≈10 20 eV studied by the methods of extensive air showers is very small. For example, only one particle with E≈ 10 19 eV falls on 1 m 2 at the boundary of the atmosphere in 1 million years. To register such small fluxes, 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. In 2016, various groups of scientists registered, according to various estimates, from 10 to 20 events generated by particles with maximum energies up to 3∙10 20 eV at giant installations for recording extensive air showers.

Observations in the cosmophysical aspect are carried out by 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 the worldwide network of neutron monitors, muon telescopes, and other detectors. However, terrestrial installations, due to atmospheric absorption, 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 plane of the ecliptic), since 1994 they have been held over the poles of the Sun (Ulysses spacecraft, "Ulyses"). 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 vehicles appear to be 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. They are formed during 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 cosmic ray variations in the past and about solar-terrestrial relationships. For example, according to the content of radiocarbon 14 C in annual tree rings ( radiocarbon dating) 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 sediments, it is possible to reconstruct the pattern 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 became 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 exhibited on satellites and returned to Earth, in the helmets of astronauts who worked in open space, etc. An indirect method is also used to study cosmic rays from the ionization effects they cause in the lower part of the ionosphere, especially in polar latitudes (for example, the effect of enhancing the 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. By 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 when solar cosmic rays enter the atmosphere.

Origin of cosmic rays

Due to the high isotropy of cosmic rays, observations near the Earth do not allow us to establish where they are formed and how they are distributed in the Universe. These questions were first answered by radio astronomy 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) as they move in the magnetic fields of the Galaxy. Such electrons, which are one of the components of cosmic rays, occupy an extended region that covers 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 small mass, electrons, unlike heavier particles, intensely radiate radio waves and thereby reveal themselves in remote 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” (bent sharply) due to the interaction of 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 no more than 50 Mpc away from us. In this case, there is practically no interaction of cosmic rays with photons of the cosmic microwave background 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 "Project Auger" seem to indicate for the first time 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 an energy of more than 10 20 eV, which is much higher than the spectrum cutoff due to the GZK effect. Various ideas have been put forward to resolve the GZK paradox. One of the hypotheses is related to the possible violation of the Lorentz invariance at superhigh energies, within the framework of which neutral and charged π-mesons can be stable particles at energies above 10 19 eV and be part of the 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 He, C, N, O, Ne, and Ar atoms. The anomalous behavior manifests itself in the fact that, in the energy range from several to several tens of MeV/nucleon, the particle spectrum differs significantly from the spectrum of galactic cosmic rays (Fig. 4). An increase in the particle flux 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 the data for June 2008 obtained from the Voyager-1 spacecraft, an increase in the flux of relatively low-energy cosmic rays (a few to tens of MeV, Fig. 5) was noted. These first data on cosmic rays, obtained directly from the interstellar medium, raise new questions about the sources and nature (generation mechanisms) of the anomalous component of cosmic rays.

Cosmic ray acceleration mechanisms

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 to explain the most essential facts. These should primarily include the value of 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. supernovae. The requirements for the energy power of sources that generate cosmic rays are very high (the power of generating 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 an energy of the order of 1044 J is released during an explosion, and explosions occur with a frequency of 1 time in 30–100 years, then their total power is about 1035 W, and only a few percent of the energy of a supernova explosion is sufficient to provide the required power of cosmic rays.

In this case, 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 a supernova) must be transferred to individual charged particles, while providing such 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 even 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). 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 (the mechanism proposed by E. Fermi, 1949), which leads to particle acceleration. With an increase in the number of shock wave front crossings, the probability of leaving the acceleration region also increases, so that as the energy increases, the number of particles falls 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 .

With some model assumptions, the proposed scheme gives the value of the maximum energy 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) spectral indices, a significant softening of the spectrum is required during the propagation of cosmic rays. Such softening 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 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 formed during the collision of galaxies. Such an event can occur with a frequency of about 1 time in 5·10 8 years; the maximum attainable 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 related to the consideration of acceleration by shock waves caused by the accretion of matter in galactic clusters. The highest estimates (up to energies of the order of 10 21 eV) can be obtained within 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 as a result of decays or annihilation of the so-called. topological defects (cosmic strings, monopoles, etc.) that appeared 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. The information "recorded" and "carried" by cosmic ray particles on their way to the Earth is deciphered in the study of cosmic ray variations - space-time changes in the cosmic ray flux under the influence of dynamic, electromagnetic and plasma processes in interstellar space, inside the heliosphere (in the flow 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 particles of cosmic rays are so high that they will remain out of competition for a long time compared to particles accelerated by the most powerful laboratory accelerators. Thus, the maximum energy of particles (protons) obtained in most modern ground-based accelerators does not generally exceed 10 12 eV. Only on June 3, 2015 at CERN at the Large Hadron Collider for the first time it was possible to accelerate protons to energies of 1.3∙10 13 eV (with a design maximum energy of 1.4∙10 13 eV).

Observations on various cosmic scales (the Galaxy, the Sun, the Earth's magnetosphere, etc.) show that particle acceleration occurs in the cosmic plasma wherever there are sufficiently intense inhomogeneous motions and magnetic fields. However, in large numbers and to very high energies, particles can only be accelerated where a 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 is still 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 unambiguous 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 make it possible to obtain information on hadron interactions up to an energy of ~10 17 eV and significantly narrow the current uncertainty that arises when extrapolating phenomenological models of hadron interactions to the region of superhigh energies. The next generation of facilities for studying extensive air showers should provide precision studies of the energy spectrum and composition of cosmic rays in the energy range of 10 17–10 19 eV, where, apparently, the transition from galactic cosmic rays to cosmic rays of extragalactic origin takes place.

Along with the huge role of cosmic rays in astrophysical processes, their importance 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 the radiation safety of astronauts).

In the beginning. 21st century Increasing attention is being drawn to the possible role of cosmic rays in atmospheric and climatic processes. Although the energy density of cosmic rays is small compared to the enormous energy of various atmospheric processes, in some of them cosmic rays apparently play a decisive role. In the earth's atmosphere at altitudes less than 30 km, cosmic rays are the main source of ion production. The processes of condensation and formation of water droplets largely depend on the density of ions. Thus, during decreases in the intensity of galactic cosmic rays in the region of disturbances in the solar wind in interplanetary space caused by solar flares (the so-called Forbush effect), cloudiness and the level of precipitation decrease. After solar flares and the arrival of solar cosmic rays on Earth, the amount of cloudiness and the level of precipitation 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 streams 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 lightning electricity. In the beginning. 21st century the influence of cosmic rays on the concentration of ozone and on 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 links. 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.

It is customary to call cosmic rays a set of flows of high-energy atomic nuclei, mainly protons, falling to the Earth from world space, and the secondary radiation they form in the earth's atmosphere, in which all currently known elementary particles are found.

§ 54. DISCOVERY OF COSMIC RAYS

Research on cosmic rays began in the first years of our century in connection with the study of the cause of the continuous leakage of the charge of electroscopes. A hermetically sealed electroscope discharged even with the most perfect insulation.

In 1910-1925. It has been shown by various experiments in balloons and underground that this is due to some strongly penetrating radiation which originates somewhere outside the earth and whose intensity decreases as it penetrates the atmosphere. It causes the ionization of the air in the ionization chamber and the consequent discharge of the electroscopes. Millikan called this radiation flux cosmic rays.

In further experiments, a change in the intensity of cosmic radiation (density of the particle flux) was established depending on the height of observation (Fig. 105).

Rice. 105. Dependence of the number of cosmic particles on height in relative units)

The intensity of cosmic rays increases relatively rapidly up to approximately the height above sea level, then the growth rate

slows down and at altitude the intensity reaches its maximum value. When ascending to high altitudes, its decrease is observed, and starting from a height, the intensity of cosmic rays remains constant. As a result of numerous experiments, it has been established that cosmic rays come to the surface of the Earth from all sides evenly and there is no place in the Universe that could be called a source of cosmic rays.

In the study of cosmic rays, many fundamentally important discoveries were made. Thus, in 1932, Anderson discovered the positron in cosmic rays, which was predicted by Dirac's theory. In 1937, Anderson and Niedermeier discovered -mesons and indicated the type of their decay. In 1947, Powell discovered -mesons, which, according to Yukawa's theory, were necessary to explain nuclear forces. In 1955, the presence of K-mesons in cosmic rays, as well as heavy neutral particles with a mass exceeding the mass of a proton - hyperons, was established. Studies of cosmic rays have led to the need to introduce a quantum characteristic called strangeness. Experiments with cosmic rays also raised the question of the possibility of parity nonconservation. In cosmic rays, for the first time, processes of multiple generation of particles in a single collision event were discovered.

Recent studies have made it possible to determine the effective cross section for the interaction of high-energy nucleons with nuclei. Since cosmic rays contain particles with energies reaching that, cosmic rays are the only source of information about the interaction of particles of such high energy.

The use of rockets and artificial satellites in the study of cosmic rays led to new discoveries - the discovery of the Earth's radiation belts. The ability to explore primary cosmic radiation outside the earth's atmosphere has created new methods for studying galactic and intergalactic space. Thus, studies of cosmic rays, having moved from the field of geophysics to the field of nuclear physics and elementary particle physics, are now closely uniting the study of the structure of the microcosm with the problems of astrophysics.

In connection with the creation of accelerators at energies of dozens, the center of gravity of the nuclear direction in cosmic ray physics has moved to the field of superhigh energies, where studies of nuclear interactions, the structure of nucleons and other elementary particles continue. In addition, an independent direction arose - the study of cosmic rays in the geophysical and astrophysical aspects. The subject of research here are: primary cosmic rays near the Earth (chemical composition, energy spectrum, spatial distribution); sun rays (their generation, movement to the Earth and influence on the earth

ionosphere); influence on cosmic rays of the interplanetary and interstellar medium and magnetic fields; radiation belts near the Earth and other planets; origin of cosmic rays. The most important means of studying these problems is a detailed study of the various variations in the cosmic ray flux observed on the Earth and near it.

K. l. resemble a highly rarefied relativistic gas, the particles of which practically do not interact with each other, but experience rare collisions with the matter of the interstellar and interplanetary media and the influence of space. magn. fields. As a part of K. l. protons predominate, there are also electrons, nuclei of helium and heavier elements (up to nuclei of elements from 30). Electrons in K. l. hundreds of times less than protons (in the same energy range). Particles K. l. have huge kinetic energies (up to eV). Although the total flow of K. l. the Earth is small [only 1 particle / (cm 2 s)], their energy density (approx. 1 eV / cm 3) is comparable (within our Galaxy) to the energy density of the total e-mag. radiation of stars, energy of thermal motion of interstellar gas and kinetic. the energy of its turbulent motions, as well as the energy density of the magnetic field of the Galaxy. It follows from this that K. l. must play a large role in the processes taking place in interstellar space.

Dr. an important feature of K. l. - 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 the thermal motion of particles is eV. Main The same number of cosmic rays observed near the earth has energies of 108 eV and higher. This means that K. l. acquire energy in specific astrophysical. processes el.-magn. and plasma nature.

Studying To. l. gives valuable information about el.-mag. fields in various areas of outer space. Information "recorded" and "carried" by particles of cosmic rays. on their way to the Earth, is deciphered in the study - spatio-temporal changes in the flow of K. l. under the influence of dynamic el.-magnet. and plasma processes in interstellar and near-Earth space.

On the other hand, as a natural source of high-energy particles, cosmic rays play an indispensable role in the study of the structure of matter and interactions between elementary particles. Energy of individual particles K. l. are so large that they will remain out of competition for a long time compared to particles accelerated (to energies ~ 10 12 eV) by the most powerful laboratory accelerators.

2. Methods for studying cosmic rays

Invading the Earth's atmosphere, primary cosmic rays. destroy the nuclei of the most common elements in the atmosphere - nitrogen and oxygen - and give rise to a cascade process (Fig. 1), in which all currently known elementary particles participate. It is customary to characterize the path traversed by a particle of cosmic rays. in the atmosphere before the collision, the amount of matter in grams enclosed in a column with a cross section of 1 cm 2, i.e. express the range of particles in g / cm 2 of the atmospheric substance. This means that after passing through the atmosphere X(in g / cm 2) in a proton beam with initial intensity I 0 the number of protons that have not experienced collisions will be equal to , where - cf. particle range. For protons, to-rye make up the majority of primary cosmic rays, in air is approximately 70 g / cm 2; for helium nuclei 25 g/cm2, for heavier nuclei even less. The first collision (70 g/cm 2 ) with atmospheric particles is experienced by protons at an average altitude of 20 km. The thickness of the atmosphere at sea level is equivalent to 1030 g/cm2, i.e. corresponds to about 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, K. l. are detected only by the weak effects of ionization created by secondary particles.

At the beginning of the 20th century in experiments with electroscopes and ionization. the chambers detected a permanent residual ionization of the gases, caused by some very penetrating radiation. Unlike radiation from radioactive substances in the environment, even thick layers of lead could not stop penetrating radiation. The extraterrestrial nature of the detected penetrating radiation was established in 1912-14. Austrian physicist W. Hess, German. scientist W. Kolhörster and other physicists who rose from the ionization. balloon cameras. It was found that with increasing distance from the Earth's surface, the ionization caused by cosmic rays increases, for example. at an altitude of 4800 m - four times, at an altitude of 8400 m - 10 times. Extraterrestrial origin K. l. finally proved R. Milliken (USA), who carried out in 1923-26. a series of experiments to study the absorption of K. l. atmosphere (it was he who introduced the term "K. l.").

Nature K. l. up to the 40s. remained unclear. During this time, the nuclear direction 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 (raised on balloons into the stratosphere), led, in particular, to the discovery of new elementary particles - the positron (1932), muon (1937), pi-mesons (1947).

Systematic study of the influence of geomagnetic. fields on the intensity and direction of arrival of primary K. l. showed that the vast majority of particles K. l. has posit. charge. The east-west asymmetry of the cosmic rays is connected with this: due to the deflection of charged particles in the magnetic field. more particles come from the west than from the east.

The use of photographic emulsions made it possible in 1948 to establish the nuclear composition of primary cosmic rays: traces of nuclei of heavy elements up to iron were found (primary electrons in the composition of cosmic rays were first recorded in stratospheric measurements only in 1961). Since the end of the 40s. the problems of the origin and temporal variations of cosmic rays gradually came to the fore. (cosmophysical aspect).

Nuclear Physics research K. l. are carried out mainly with the help of large-area counter installations designed to register the so-called. broad air showers of secondary particles, which are formed by the intrusion of one primary particle with an energy of eV. Main the purpose of such observations is to study the characteristics of an elementary act of nuclear interaction at high energies. Along with this, they provide information about the energy. spectrum K. l. at eV, which is very important for the search for sources and mechanisms of acceleration of cosmic rays.

Observations K. l. in cosmophysics. aspect are carried out by very diverse methods - depending on the energy of the particles. Variations K. l. with eV are studied using data from a worldwide network of neutron monitors (the neutron component of cosmic rays), counter telescopes (the muon component of cosmic rays), and other detectors. However, ground-based installations are insensitive to particles with MeV due to atmospheric absorption. Therefore, devices for detecting such particles are raised on balloons into the stratosphere up to altitudes of 30-35 km.

Extra-atmospheric measurements of the flux of cosmic rays. 1-500 MeV are carried out using geophysical. missiles, satellites and other spacecraft. Direct observations K. l. in interplanetary space have so far been carried out only near the plane of the ecliptic up to a distance of ~ 10 AU. e. from the Sun.

A number of valuable results were obtained by the method of cosmogenic isotopes. They are formed during the interaction of K. l. with meteorites and space. dust, with the surface of the Moon and other planets, with the atmosphere or matter of the Earth. Cosmogenic isotopes carry information about variations in cosmic rays. in the past and about . According to the content of radiocarbon 14 C in the annual rings of trees, it is possible, for example, to study variations in the intensity of K. l. over the course of several the last thousand years. Other long-lived isotopes (10 Be, 26 Al, 53 Mn, and others) contained in meteorites, lunar soil, and deep sea sediments can be used to reconstruct the pattern of changes in the intensity of cosmic rays. for millions of years.

With the development of space technology and radio-chem. methods of analysis, it became possible to study the characteristics of K. l. along the tracks (traces) created by the nuclei of cosmic rays. in meteorites, lunar matter, in special. target samples exhibited on satellites and returned to Earth, in the helmets of astronauts who worked in outer space, etc. The indirect method of studying is also used To. l. on the effects of ionization caused by them in the lower part of the ionosphere, especially in polar latitudes. These effects are significant. arr. during the invasion of the earth's atmosphere solar cosmic rays.

3. Cosmic rays near the Earth

Tab. 1. Relative abundance of nuclei in cosmic rays, on the Sun and stars (on average)

Element	Solar C.l.	Sun (photosphere)	Stars	Galactic cosmic rays
1H	4600*	1445	925	685
2 He (-particle)	70*	91	150	48
3Li	?			0,3
4 Be-5 B	0,02			0,8
6C	0,54*	0,6	0,26	1,8
7 N	0,20	0,1	0,20	0,8
8 O**	1,0*	1,0	1,0	1,0
9F		10 -3		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	0,040	0,32
13 Al	?	0,002	0,004	0,06
14Si	0,13*	0,065	0,045	0,12
15 P - 21 Sc	0,06	0,032	0,024	0,13
16S-20Ca	0,04*	0,028	0,02	0,11
22Ti- 28Ni	0,02	0,006	0,033	0,28
26 Fe	0,15*	0,05	0,06	0,14

* Observational data for the interval =1-20 MeV/nucleon, the rest of the figures in this column refer mainly to >40 MeV/nucleon. The accuracy of most values ​​in the table as a whole is from 10 to 50%. ** The abundance of oxygen nuclei is taken as unity.

The most important characteristics of K. l. yavl. their composition (distribution by masses and charges), energetic. spectrum (energy distribution) and degree of anisotropy (arrival distribution). The relative content of nuclei in K. l. are given in Table 1. From Table. 1 shows that in the composition of K. l. galactic the origin of much more light nuclei ( Z= 3–5) than in solar cosmic rays. and on average in the stars of the Galaxy. In addition, they contain significantly more heavy poisons (20) compared to their natural abundance. Both of these differences are very important for clarifying the question of the origin of K. l.

The relative numbers of particles with different masses in cosmic rays. are given in table. 2.

Tab. 2. Composition and some characteristics of cosmic rays with energies of 2.5 GeV/nucleon

pprotons1 1 1300 10000 10000 -particlehelium nuclei2 4 94 720 1600 Llight nuclei3-5 10 2,0 15 10 -4 Mmedium kernels6-9 14 6,7 52 14 Hheavy nuclei10 31 2,0 15 6 vhvery heavy nuclei20 51 0,5 4 0,06 SHthe heaviest nuclei > 30 100 ~10 -4 ~10 -3 eelectrons1 1/1836 13 100 10000

It can be seen that protons predominate in the flow of primary cosmic rays; they make up more than 90% of the number of all particles. In relation to protons, -particles make up 7%, electrons ~ 1% and heavy nuclei - less than 1%. These figures refer to particles with an energy of 2.5 GeV/nucleon measured near the Earth at the minimum of solar activity, when the observed energetic. the spectrum can be considered close to the unmodulated spectrum of cosmic rays. in interstellar space.

Integral energy. spectrum K. l. align="absmiddle" width="145" height="22"> [particles/(cm 2 s)] reflects the dependence of the number of particles I with higher energy ( I 0 - normalization constant, +1 - spectrum index, minus sign indicates that the spectrum has a falling character, i.e. with increase in intensity To. l. decreases). The differential representation of the spectrum [particles / (cm 2 s MeV)] is also often used, which reflects the dependence on the number of particles per unit energy interval (1 MeV).

The differential spectrum, in comparison with the integral spectrum, makes it possible to reveal finer details of the energetics. distribution K. l. This can be seen from fig. 2, which shows the differential spectrum of cosmic rays observed near the Earth in the range from about 10 6 to eV. Particles K. l. with energies falling within this interval are subject to the influence of solar activity, so the study of energy. spectrum K. l. in the range 10 6 -10 11 eV is extremely important for understanding the penetration of cosmic rays. from interstellar to interplanetary space, the interactions of cosmic rays. with interplanetary magnet. field (IMF) and , for the interpretation of solar-terrestrial relations.

Before the start of extra-atmospheric and extra-magnetospheric observations, K. l. the question of the shape of the differential spectrum in the eV region seemed quite clear: the spectrum near the Earth has a maximum near 400 MeV/nucleon; the unmodulated spectrum in interstellar space must have a power-law form; there should be no galaxies in interplanetary space. K. l. small energies. Direct measurements K. l. in the range from 10 6 to 10 8 eV showed, contrary to expectations, that, starting from about = 30 MeV (and lower), the intensity of the cosmic rays. grows again, i.e. a characteristic dip in the spectrum was found. Probably, the failure is the result of enhanced modulation of the cosmic rays. in the eV region, where particle scattering by IMF inhomogeneities is most efficient.

It has been established that at eV the spectrum of K. l. is no longer subject to modulation, and its slope corresponds to a value of 2.7 up to eV. At this point, the spectrum undergoes a break (the index increases to =3.2-3.3). There are indications that at the same time as a part of K. l. the proportion of heavy nuclei increases. However, data on the composition of K. l. in this energy region are still very scarce. With align="absmiddle" width="118" height="17"> eV, the spectrum should cut off abruptly due to the escape of particles into the intergalactic space. space and interactions with photons. The flux of particles in the region of ultrahigh energies is very small: on average, no more than one particle per eV falls on an area of ​​10 km 2 per year.

For K. l. eV is characterized by high isotropy: with an accuracy of 0.1%, the particle intensity is the same in all directions. At higher energies, the anisotropy increases and in the range of eV reaches several times. tens of % (Fig. 3). An anisotropy of ~ 0.1% with a maximum near 7 p.m. sidereal time corresponds to the predominant direction of motion of the cosmic rays. along magnetic field lines. galactic fields. spiral arm, in which the Sun is located. As the energy of the particles increases, the time of the maximum shifts to 1 pm sidereal time, which corresponds to the presence of a drift flux of cosmic rays. with eV from the Galaxy across the magnetic field lines.

4. Origin of cosmic rays

Due to the high isotropy of K. l. Observations near the Earth do not allow us to establish where they are formed and how they are distributed in the Universe. These questions were answered by radio astronomy in connection with the discovery of space. in the Hz radio frequency range. This radiation is created by very high energy electrons as they move in the magnetic field. field of the galaxy.

The frequency at which the intensity of radio emission is maximum is related to the strength of the magnetic field. fields H and electron energy by the ratio (Hz), where is the pitch angle of the electron (the angle between the electron velocity vector and the vector H). Magn. field of the Galaxy, measured several. methods, has the value of E. On average, at E and = 0.5, eV, i.e. radio-emitting electrons must have the same energies as the main. mass of cosmic rays observed near the earth. These electrons, which are one of the components of cosmic rays, occupy an extended region that embraces the entire galaxy and is called the galactic region. halo. In interstellar magn. In fields, electrons move like other high-energy charged particles - protons and heavier nuclei. The only difference is that, due to their low mass, electrons, in contrast to heavier particles, intensely radiate radio waves and thereby reveal themselves in remote parts of the galaxy, being an indicator of cosmic rays. at all.

In addition to the general galactic synchrotron radio emission, its discrete sources were discovered: shells, the core of the Galaxy,. It is natural to expect that all these objects-sources of cosmic rays.

Until the beginning of the 70s. 20th century many researchers believed that K. l. with align="absmiddle" width="89" height="17"> eV have mostly metagalactic. origin. At the same time, the absence of known galaxies was pointed out. sources of particles with up to 10 21 eV and the difficulties associated with the problem of their containment in the Galaxy. In connection with the discovery of pulsars (1967), a number of possible mechanisms for accelerating even very heavy nuclei to superhigh energies were considered. On the other hand, the data obtained indicate that the electrons observed near the Earth are formed and accumulated in the Galaxy. There is no reason to think that protons and heavier nuclei behave differently in this respect. Thus, the theory of galactic is justified. origin K. l.

Indirect confirmation of this theory was obtained from data on the distribution of cosmic sources over the celestial sphere. gamma radiation. This radiation arises due to the decay of -mesons, which are formed during collisions of cosmic rays. with particles of interstellar gas, and also due to bremsstrahlung of relativistic electrons in their collisions with particles of interstellar gas. Gamma rays are not affected by magnets. fields, so the direction of their arrival directly points to the source. In contrast to the almost isotropic distribution of cosmic rays observed inside the solar system, the distribution of gamma radiation over the sky turned out to be very uneven and similar to the distribution of supernovae over galaxies. longitude (Fig. 4). A good agreement between the experimental data and the expected distribution of gamma radiation over the celestial sphere is a strong evidence that the main. The source of cosmic rays is supernovae.

Theory of origin K. l. relies not only on the hypothesis of galactic the nature of the sources of K. l., but also on the idea that K. l. for a long time are kept in the Galaxy, slowly flowing into the intergalactic. space. Moving in a straight line, K. l. would have left the galaxy after a few. thousand years after the moment of generation. On a galactic scale, this time is so short that it would be impossible to make up for losses with such a rapid leak. However, in the interstellar magnetic field with highly entangled lines of force has a complex character, reminiscent of the diffusion of molecules in a gas. As a result, the leakage time K. l. from the Galaxy turns out to be thousands of times greater than during rectilinear motion. The foregoing concerns the parts of particles K. l. (with eV). Particles with a higher energy, the number of which is very small, are weakly deflected by the galactic. magn. field and leave the Galaxy relatively quickly. Apparently, a break in the spectrum of cosmic rays is associated with this. at eV.

The most reliable estimate of the leakage time of K. l. from the Galaxy is obtained from data on their composition. In K. l. in a very large number (compared with the average abundance of elements) there are light nuclei (Li, Be, B). They are formed from heavier nuclei of cosmic rays. when the latter collide with the nuclei of atoms of interstellar gas (mainly hydrogen). In order for light nuclei to be present in an observable amount, K. l. during their movement in the Galaxy, a thickness of interstellar matter of approx. 3 g/cm. According to data on the distribution of interstellar gas and remnants of supernova explosions, the age of the spacecraft. does not exceed 30 million years.

In favor of supernovae as the main The source of cosmic rays, in addition to data from radio, x-ray, and gamma-ray astronomy, is also indicated by estimates of their energy release during flares. Supernova explosions are accompanied by the ejection of huge masses of gas, which form a large brightly luminous and expanding shell (nebula) around the exploding star. The total energy of the explosion, which is spent on radiation and kinetic. the energy of gas expansion can reach 10 51 -10 52 erg. In our Galaxy, according to the latest data, supernovae erupt on average at least once every 100 years. If we attribute the flare energy of 10 51 erg to this time interval, then cf. flash output will be approx. erg/s. On the other hand, to maintain modern energy density K. l. OK. 1 eV/cm power of sources K. l. at cf. lifetime K. l. in the Galaxy, years must be at least 10 40 erg/s. It follows from this that in order to maintain the energy density of cosmic rays. on modern level is enough for them to be transferred only a few. % power of a supernova explosion. However, radio astronomy can only directly detect radio-emitting electrons. Therefore, it is not yet possible to state definitively (although this seems quite natural, especially in the light of the achievements of gamma-ray astronomy) that a sufficient number of protons and heavier nuclei are also generated during supernova explosions. In this regard, the search for other possible sources of cosmic rays has not lost its significance. Of great interest in this regard are pulsars (where, apparently, acceleration of particles to superhigh energies is possible) and the region of galaxies. nuclei (where explosive processes of much greater power are possible than supernova explosions). However, the generation power of K. l. galactic apparently does not exceed the total power of their generation during supernova outbursts. In addition, most of the cosmic rays formed in the nucleus will leave the disk of the Galaxy before reaching the vicinity of the Sun. Thus, we can assume that supernova explosions yavl. the main, though not the only source of K. l.

5. Cosmic ray acceleration mechanisms

The question of possible mechanisms of particle acceleration up to energies ~ 10 21 eV is still far from finished in detail. solutions. However, in general terms, the nature of the acceleration process is already clear. In an ordinary (non-ionized) gas, the redistribution of energy between particles occurs due to their collisions with each other. In rarefied space In plasma, collisions between charged particles play a very small role, and the change in energy (acceleration or deceleration) of an individual particle is due to its interaction with the el.-magnet. fields arising from the movement of all plasma particles surrounding it.

Under normal conditions, the number of particles with energies noticeably higher than cf. the energy of the thermal motion of plasma particles is negligible. Therefore, particle acceleration should start practically from thermal energies. In space Plasma (electrically neutral) cannot exist any significant electrostatic. fields, to-rye could accelerate charged particles due to the potential difference between the points of the field. However, in the plasma can occur electric. fields of impulsive or inductive character. Pulse electric fields appear, for example, when a neutral current sheet is broken, which occurs in the area of ​​​​contact of the magnetic. fields of opposite polarity (see). Induction electric the field appears when the magnetic strength increases. fields with time (betatron effect). In addition to pulsed fields, the initial stage of acceleration can be due to the interaction of accelerated particles with electric fields of plasma waves in regions with intense turbulent plasma motion.

In space, apparently, there is a hierarchy of accelerating mechanisms, which operate in various combinations or in various sequences, depending on the specific conditions in the field of acceleration. Acceleration pulse electric. field or plasma turbulence contributes to the subsequent acceleration by the induction (betatron) mechanism or the Fermi mechanism.

Some features of the process of particle acceleration in space are associated with the behavior of plasma in magn. field. Space magn. fields exist in large volumes of space. particle with a charge Ze and momentum p moves in magnetic field H along a curved path with an instantaneous radius of curvature
,
Where R = cp/Ze- magn. the stiffness of the particles (measured in volts), - the pitch angle of the particle. If the field changes little at distances comparable to , then the particle trajectory has the form of a helix winding around the magnetic field line. fields. In this case, the field lines of force are, as it were, attached to the plasma (frozen into the plasma) - the displacement of any section of the plasma causes a corresponding displacement and deformation of the magnetic field lines. fields and vice versa. If sufficiently intense motions are excited in the plasma (such a situation arises, for example, as a result of a supernova explosion), then there are many such randomly moving regions of the plasma. For clarity, it is convenient to consider them as separate plasma clouds moving relative to each other at high speeds. Main the mass of plasma particles is held in clouds and moves with them. However, a small number of high-energy particles, for which the radius of curvature of the trajectory in magn. the plasma field is comparable to the size of the cloud or exceeds it, getting into the cloud, does not remain in it. These particles are only deflected by the magnetic. field of the cloud, there is a kind of collision of the particle with the cloud as a whole and the scattering of particles on it (Fig. 5). Under such conditions, the particle effectively exchanges energy with the entire cloud at once. But the kinetic the energy of the cloud is very high and, in principle, the energy of the accelerated thus particles can grow indefinitely until the particle leaves the region with intense plasma motions. This is the essence of statistics. the acceleration mechanism proposed by E. Fermi in 1949. Similarly, particles are accelerated when they interact with powerful shock waves (eg, in interplanetary space), in particular, when two shock waves approach each other, forming reflective magnetic fields. "mirrors" (or "walls") for accelerated particles.

All acceleration mechanisms lead to a spectrum of cosmic rays, in which the number of particles decreases with increasing energy. This is where the similarities between the mechanisms end. Despite intensive theoretical and experimental studies, until a universal acceleration mechanism or a combination of mechanisms has been found that could explain all the features of the spectrum and charge composition of cosmic rays. In the case of, for example, a pulsed electric fields E hardness increment rate R is determined by the ratio dR/dt = cE, i.e. does not depend on the original magnetic. particle stiffness. In this case, all particles in the field of action are accelerated E , their composition will reflect the composition of the initial plasma, and the spectrum will have the form D(R)~exp -(R/R 0), where R 0 - characteristic rigidity of the spectrum.

When accelerated by plasma waves, particles with an energy of only a few times can be accelerated. times more thermal. The number of such particles is not too small, but the acceleration conditions will depend significantly on the type of particles, which should lead to a strong change in their composition compared to the composition of the initial plasma. The spectrum of accelerated protons, however, in this case can be ~ exp -(R/R 0).

The betatron mechanism, which is based on the preservation of adiabatic particle motion invariant = const, gives a power-law spectrum and is not selective with respect to the type of particles, but its efficiency is proportional to the magnetic. particle stiffness ( dR/dt ~ R), i.e. its action requires preliminary acceleration (injection).

The Fermi acceleration mechanism gives a power-law energy. spectrum, however, it is selective with respect to the sort of particles. Acceleration by shock waves in space. plasma also leads to a power-law energetic. spectrum, and theoretically. calculations give an index = 2.5, which agrees rather well with the observed shape of the spectrum of cosmic rays. Thus, the theory of acceleration, unfortunately, allows an ambiguous approach to the interpretation of the observed spectra of accelerated particles (in particular, solar cosmic rays).

Processes of acceleration by impulse electric. fields near the zero lines of the magnetic. fields are observed during flares on the Sun, when for several. min particles appear, accelerated to an energy of several. GeV. Near pulsars, in the shells of supernovae in the Galaxy, as well as in the extragalactic. objects - radio galaxies and quasars - this process can also play the role of DOS. acceleration mechanism, or at least the role of an injector. In the latter case, the injected particles are accelerated up to max. observed in K. l. energies as a result of interactions with waves and with inhomogeneities of the magnetic. fields in turbulent plasma.

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

Along with the huge role of K. l. in astrophysical processes, it is necessary to note their importance for studying the distant past of the Earth (climate changes, the evolution of the biosphere, etc.) and for solving some practical problems. tasks of the present (ensuring the radiation safety of cosmonauts, assessing the possible contribution of cosmic rays to meteorological effects, etc.).

Lit.:
Ginzburg V.L., Syrovatsky S.I., Origin of cosmic rays, M., 1963; Miroshnichenko L.I., Cosmic rays in interplanetary space, M., 1973; Dorman L.I., Experimental and theoretical foundations of astrophysics of cosmic rays, M., 1975; Toptygin I. N., Cosmic rays in interplanetary magnetic fields, M., 1983.

(L.I. Miroshnichenko)