In 1958, the Americans launched an artificial Earth satellite “Explorer 1” equipped with a Geiger counter. At perigee, the measuring device showed the calculated radiation level. After the aircraft reached its climax, the Geiger counter stopped transmitting the signal.
US astrophysicist James Alfred Van Allen (English version – Van Allen) suggested that the lack of readings is due to increased radiation levels. Further research by American and Russian scientists confirmed this hypothesis. It turned out that the planet is surrounded by radioactive belts, in which electrons and protons of the solar wind, charged with energy up to 3 MeV, are concentrated and held.
The discovery was of great importance for the further exploration of space. The regions of the magnetosphere that hold elementary particles are called the “Van Allen radiation belts”. The open phenomenon is typical not only for the Earth, but also for other planets with a powerful magnetic field (Jupiter, Neptune, etc.).
The structure of the radiation belt
The area of the magnetic sphere holding charged elementary particles is similar in shape to a torus. There is an internal (up to 4 thousand km) and external (up to 17 thousand km) radioactive belt. The first region consists mainly of positively charged elementary particles with energies of tens of MeV. The second belt contains low-energy electrons. There is a “gap” between the inner and outer zones of the magnetosphere, which is in the interval from two to three radii of the planet (the so-called “safe area”).
The altitude of the lower part of the Earth’s inner radiation belt changes in longitude at the same latitude. The difference in distances is due to the tilt of the magnetosphere relative to the axis of rotation of the planet. The change in the height of the Van Allen radiation belt in longitude at different latitudes is associated with different sizes of the force contours of the Earth’s magnetic field. The inner region of the magnetosphere is stable, while the outer one is subject to strong vibrations.
Scientists continue to study the radioactive fields of the Earth. Physicists and astronomers conduct experiments in which the behavior of elementary particles in electric and magnetic fields, plasma and interplanetary medium is investigated. The data obtained make it possible to predict space weather and determine the minimum latitudes to which various plasma structures located in the magnetosphere approach the planet.
Influence of radiation fields on flying vehicles and the health of astronauts
Spaceships and satellites moving at an altitude of more than 2000 km inevitably fall under the influence of the Van Allen belts. Intense radiation damages solar panels, electronic components and measuring instruments. Special microcircuits are being developed for rockets and satellites, which are produced using the silicon-on-insulator technology.
These electronic components are resistant to ionizing radiation present in the radiation belt around the Earth. To protect the hulls of spacecraft from ionizing radiation, special coatings made of alloys of iron, aluminum and beryllium are used. Materials with a high hydrogen content (eg polyethylene) are also used.
Ionizing radiation has a harmful effect on astronauts. Radiation in the Van Allen belt destroys tissue, disrupts metabolism, lowers immunity and increases the risk of developing malignant neoplasms. The trajectories of controlled spacecraft are aligned in such a way as to minimize the presence of astronauts in the radiation belts. This approach was used by American scientists when planning a flight to the moon. The participants of the Apollo program, who visited the charged magnetosphere, received an annual absorbed dose of 2-11.4 mSv (the safe level of radiation is 50 mSv).
Van Allen belts and antimatter: myths and reality
In 2011, the scientific journal Astrophysical Journal Letters published an article on the results of the international experiment PAMELA. With the help of a powerful spectrograph, scientists were able to detect a layer of antimatter between the Earth’s inner and outer radiation belt. A high concentration of antiprotons was recorded by instruments in the area of the South Atlantic Magnetic Anomaly.
The mass of antiprotons is held by the magnetosphere of our planet at a distance of several hundred kilometers from the earth’s surface. At low altitudes, anti-elements are neutralized, which interact with ordinary particles. Van Allen belts are a powerful source of antimatter, which is considered one of the main mysteries of the universe. NASA Institute experts believe that antiprotons will become a new type of fuel for spacecraft in the future.