Electron fluxes in the Earth's radiation belts arise as a result of the interactions of cosmic rays with atoms in the upper layers of the planet's atmosphere, "knocking out" neutrons from them, according to an article published in the journal Nature.
“For the first time, we were able to detect the creation of these high-energy electrons at the inner edge of the Van Allen belts. We managed to solve the riddle over which physicists have puzzled for almost six decades,”said Xinlin Li from the University of Colorado in Boulder (USA).
The Earth, unlike Venus and a number of other planets of the solar system, has its own magnetic field, which is generated as a result of the movement of liquid flows of metal in its core. This magnetic field acts as a kind of "shield" that reflects cosmic rays, high-energy charged particles, and protects the Earth from the solar wind and coronal mass ejections on the Sun.
Traces of its existence are the so-called van Allen belts - two areas at altitudes of about 6 thousand and 60 thousand kilometers from the Earth's surface, where there are a large number of high-energy protons and electrons, "caught" by the Earth's magnetic field and moving in a kind of magnetic trap. Their interaction with the atmosphere generates beautiful auroras, and, during solar flares, leads to radio interference and other technical problems.
One of the main mysteries of the Van Allen Belts since their discovery in 1958 is where the high-energy electrons and protons that inhabit the Earth's radiation shield and generate flares at the planet's poles come from. As Lee notes, scientists have long suspected that their source is cosmic rays colliding with atoms in the atmosphere, but they did not have unequivocal evidence of this.
An additional problem is that cosmic rays, generated by supernova explosions and pulsar activity, "bombard" the Earth at approximately the same frequency, while the number and properties of electrons in the Van Allen belts can change dramatically at a very high rate. This makes many researchers doubt that these electrons arise as a result of neutron decays, which cosmic rays "knock" out of nitrogen and oxygen atoms.
To test these ideas, Lee and his students assembled the CSSWE microsatellite, equipped with miniature counterparts of the electron and proton detectors that were developed at the University of Colorado for the RBSP probes launched by NASA in August 2012 to study the structure of the Van Allen belts.
This satellite was launched into a lower orbit, and it studied not the inner layers of the Van Allen belts, but the lower edge of its first part, where, as scientists suggested, electrons and protons should be born during collisions of gas molecules and "guests from space".
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Such collisions, as scientists explain, should lead to the production of protons and electrons in very narrow energy ranges, so that they can be easily calculated and estimated how often cosmic rays collide with atmospheric atoms, and understand what role they play in filling the Van Allen belts and how they get there.
As shown by these measurements, such electrons do arise in large quantities at an altitude approximately equal to the Earth's radius, and the rate of their formation and their properties remained constant in all regions and at all altitudes. This speaks in favor of the fact that they are actually generated by cosmic rays.
Moreover, this is evidenced by the number of electrons recorded by the CSSWE - their number, as scientists note, almost ideally corresponds to how many neutrons should generate cosmic rays. All this, accordingly, testifies to the fact that almost all the electrons participating in the birth of auroras are of a truly "cosmic" origin.