The Earth's Radiation Belt (ERB), or the Van Allen belt, is the region of the nearest outer space near our planet, which looks like a ring, in which there are giant flows of electrons and protons. The earth holds them with a dipole magnetic field.
Opening
RPZ was discovered in 1957-58. scientists from the United States and the USSR. Explorer 1 (pictured below), the first US space satellite launched in 1958, has provided very important data. Thanks to an onboard experiment carried out by the Americans above the Earth's surface (at an altitude of about 1000 km), a radiation belt (internal) was found. Later, at an altitude of about 20,000 km, a second such zone was discovered. There is no clear boundary between the inner and outer belts - the first gradually turns into the second. These two zones of radioactivity differ in the degree of charge of the particles and their composition.
These areas became known as the Van Allen belts. James Van Allen is a physicist whose experiment helped themdiscover. Scientists have found that these belts consist of the solar wind and charged particles of cosmic rays, which are attracted to the Earth by its magnetic field. Each of them forms a torus around our planet (a shape that resembles a doughnut).
Many experiments have been carried out in space since that time. They made it possible to study the main features and properties of the RPZ. Not only our planet has radiation belts. They are also found in other celestial bodies that have an atmosphere and a magnetic field. The Van Allen Radiation Belt was discovered thanks to US interplanetary spacecraft near Mars. In addition, the Americans found it near Saturn and Jupiter.
Dipole magnetic field
Our planet has not only the Van Allen belt, but also a dipole magnetic field. It is a set of magnetic shells nested inside each other. The structure of this field resembles a head of cabbage or an onion. The magnetic shell can be imagined as a closed surface woven from magnetic lines of force. The closer the shell is to the center of the dipole, the greater the magnetic field strength becomes. In addition, the momentum required for a charged particle to penetrate it from the outside also increases.
So, the Nth shell has the particle momentum P . In the case when the initial momentum of the particle does not exceed P , it is reflected by the magnetic field. The particle then returns to outer space. However, it also happens that it ends up on the Nth shell. In this caseshe is no longer able to leave it. The trapped particle will be trapped until it dissipates or collides with the residual atmosphere and loses energy.
In the magnetic field of our planet, the same shell is located at different distances from the earth's surface at different longitudes. This is due to the mismatch between the axis of the magnetic field and the axis of rotation of the planet. This effect is best seen over the Brazilian Magnetic Anomaly. In this area, magnetic lines of force descend, and trapped particles moving along them may be below 100 km in height, which means they will die in the earth's atmosphere.
RPG Composition
Inside the radiation belt, the distribution of protons and electrons is not the same. The first are in the inner part of it, and the second - in the outer. Therefore, at an early stage of the study, scientists believed that there were external (electronic) and internal (proton) radiation belts of the Earth. Currently, this opinion is no longer relevant.
The most significant mechanism for the generation of particles filling the Van Allen belt is the decay of albedo neutrons. It should be noted that neutrons are created when the atmosphere interacts with cosmic radiation. The flow of these particles moving in the direction from our planet (albedo neutrons) passes through the Earth's magnetic field without hindrance. However, they are unstable and easily decay into electrons, protons, and electron antineutrinos. Radioactive albedo nuclei, which have high energy, decay inside the capture zone. This is how the Van Allen belt is replenished with positrons and electrons.
ERP and magnetic storms
When strong magnetic storms begin, these particles do not just accelerate, they leave the Van Allen radioactive belt, spilling out of it. The fact is that if the configuration of the magnetic field changes, the mirror points can be immersed in the atmosphere. In this case, the particles, losing energy (ionization losses, scattering), change their pitch angles and then perish when they reach the upper layers of the magnetosphere.
RPZ and northern lights
The Van Allen radiation belt is surrounded by a plasma layer, which is a trapped stream of protons (ions) and electrons. One of the reasons for such a phenomenon as the northern (aurora borealis) is that the particles fall out of the plasma layer, and also partly from the outer ERP. The aurora borealis is the emission of atmospheric atoms, which are excited due to collision with particles that have fallen out of the belt.
RPZ Research
Almost all the fundamental results of studies of such formations as radiation belts were obtained around the 1960s and 70s. Recent observations using orbital stations, interplanetary spacecraft and the latest scientific equipment have allowed scientists to obtain very important new information. The Van Allen belts around the Earth continue to be studied in our time. Let's briefly talk about the most important achievements in this area.
Data received from Salyut-6
Researchers from MEPhI in the early 80s of the last centuryinvestigated the flows of electrons with a high level of energy in the immediate vicinity of our planet. To do this, they used the equipment that was on the Salyut-6 orbital station. It allowed scientists to very effectively isolate the fluxes of positrons and electrons, the energy of which exceeds 40 MeV. The station's orbit (inclination 52°, altitude about 350-400 km) passed mainly below the radiation belt of our planet. However, it still touched its inner part at the Brazilian Magnetic Anomaly. When crossing this region, stationary streams consisting of high-energy electrons were found. Prior to this experiment, only electrons were recorded in the ERP, the energy of which did not exceed 5 MeV.
Data from artificial satellites of the "Meteor-3" series
Researchers from MEPhI carried out further measurements on artificial satellites of our planet of the Meteor-3 series, in which the height of circular orbits was 800 and 1200 km. This time the device has penetrated very deeply into the RPZ. He confirmed the results that were obtained earlier at the Salyut-6 station. Then the researchers obtained another important result by using the magnetic spectrometers installed at the Mir and Salyut-7 stations. It was proved that the previously discovered stable belt consists exclusively of electrons (without positrons), the energy of which is very high (up to 200 MeV).
Discovery of the stationary belt of CNO nuclei
A group of researchers from the SNNP MSU in the late 80s and early 90s of the last century carried out an experiment aimed atthe study of nuclei that are located in the nearest outer space. These measurements were carried out using proportional chambers and nuclear photographic emulsions. They were carried out on satellites of the Kosmos series. Scientists have detected the presence of streams of N, O and Ne nuclei in a region of outer space in which the orbit of an artificial satellite (inclination 52 °, altitude about 400-500 km) crossed the Brazilian anomaly.
As the analysis showed, these nuclei, whose energy reached several tens of MeV/nucleon, were not of galactic, albedo or solar origin, since they could not penetrate deeply into the magnetosphere of our planet with such energy. So scientists discovered the anomalous component of cosmic rays, captured by the magnetic field.
Low-energy atoms in interstellar matter are able to penetrate the heliosphere. Then the ultraviolet radiation of the Sun ionizes them once or twice. The resulting charged particles are accelerated by the solar wind fronts, reaching several tens of MeV/nucleon. They then enter the magnetosphere, where they are captured and fully ionized.
Quasistationary belt of protons and electrons
On March 22, 1991, a powerful flare occurred on the Sun, which was accompanied by the ejection of a huge mass of solar matter. It reached the magnetosphere by March 24 and changed its outer region. Particles of the solar wind, which had high energy, burst into the magnetosphere. They reached the area where CRESS, the American satellite, was then located. installed on itinstruments recorded a sharp increase in protons, whose energy ranged from 20 to 110 MeV, as well as powerful electrons (about 15 MeV). This indicated the emergence of a new belt. First, the quasi-stationary belt was observed on a number of spacecraft. However, only at the Mir station was it studied during its entire lifetime, which is about two years.
By the way, in the 60s of the last century, as a result of the fact that nuclear devices exploded in space, a quasi-stationary belt appeared, consisting of electrons with low energies. It lasted approximately 10 years. The radioactive fragments of fission decayed, which was the source of charged particles.
Is there an RPG on the Moon
The satellite of our planet lacks the Van Allen radiation belt. In addition, it does not have a protective atmosphere. The surface of the moon is exposed to solar winds. A strong solar flare, if it happened during a lunar expedition, would incinerate both the astronauts and the capsules, as there would be a huge stream of radiation that would be released, which is deadly.
Is it possible to protect yourself from cosmic radiation
This question has been of interest to scientists for many years. In small doses, radiation, as you know, has practically no effect on our he alth. However, it is safe only when it does not exceed a certain threshold. Do you know what the level of radiation is outside the Van Allen belt, on the surface of our planet? Usually the content of radon and thorium particles does not exceed 100 Bq per 1 m3. Inside the RPZthese figures are much higher.
Of course, the radiation belts of Van Allen Land are very dangerous for humans. Their effect on the body has been studied by many researchers. Soviet scientists in 1963 told Bernard Lovell, a well-known British astronomer, that they did not know a means of protecting a person from exposure to radiation in space. This meant that even the thick-walled shells of Soviet apparatuses could not cope with it. How did the thinnest metal used in American capsules, almost like foil, protect the astronauts?
According to NASA, it sent astronauts to the moon only when no flares were expected, which the organization is able to predict. This is what made it possible to reduce the radiation hazard to a minimum. Other experts, however, argue that it is only possible to roughly predict the date of large emissions.
The Van Allen belt and the flight to the moon
Leonov, a Soviet cosmonaut, nevertheless went into outer space in 1966. However, he was wearing a super-heavy lead suit. And after 3 years, astronauts from the United States were jumping on the lunar surface, and obviously not in heavy spacesuits. Perhaps, over the years, NASA specialists have managed to discover an ultra-light material that reliably protects astronauts from radiation? The flight to the moon still raises many questions. One of the main arguments of those who believe that the Americans did not land on it is the existence of radiation belts.
