Van Allen radiation belt

[1][2] Earth's two main belts extend from an altitude of about 640 to 58,000 km (400 to 36,040 mi)[3] above the surface, in which region radiation levels vary.

The belts endanger satellites, which must have their sensitive components protected with adequate shielding if they spend significant time near that zone.

[7] Kristian Birkeland, Carl Størmer, Nicholas Christofilos, and Enrico Medi had investigated the possibility of trapped charged particles in 1895, forming a theoretical basis for the formation of radiation belts.

[13] NASA's Goddard Space Flight Center manages the Living With a Star program—of which the Van Allen Probes were a project, along with Solar Dynamics Observatory (SDO).

[14] Radiation belts exist around other planets and moons in the solar system that have magnetic fields powerful and stable enough to sustain them.

Observations of radio emissions from highly energetic particles that are trapped in a planets magnetic field have also been used to remotely detect radiation belts, including at Jupiter [15] and at the ultracool dwarf LSR J1835+3259.

[16] It is possible that Mercury (planet) may be able to trap charged particles in its magnetic field,[17] although its highly dynamic magnetosphere (which varies on the order of minutes [18]) may not be able to sustain stable radiation belts.

Venus and Mars do not have radiation belts, as their magnetospheric configurations do not trap energetic charged particles in orbit around the planet.

[4][20] In certain cases, when solar activity is stronger or in geographical areas such as the South Atlantic Anomaly, the inner boundary may decline to roughly 200 km[21] above the Earth's surface.

Radiation belt electrons are also constantly removed by collisions with Earth's atmosphere,[30] losses to the magnetopause, and their outward radial diffusion.

Energetic (radiation) particle fluxes can increase and decrease dramatically in response to geomagnetic storms, which are themselves triggered by magnetic field and plasma disturbances produced by the Sun.

Another cause of variability of the outer belt particle populations is the wave-particle interactions with various plasma waves in a broad range of frequencies.

In a news conference by NASA's Van Allen Probe team, it was stated that this third belt is a product of coronal mass ejection from the Sun.

[34] This absence of scattering and the trapping allows them to persist for a long time, finally only being destroyed by an unusual event, such as the shock wave from the Sun.

The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment detected levels of antiprotons orders of magnitude higher than are expected from normal particle decays while passing through the South Atlantic Anomaly.

This suggests the Van Allen belts confine a significant flux of antiprotons produced by the interaction of the Earth's upper atmosphere with cosmic rays.

[42] A satellite shielded by 3 mm of aluminium in an elliptic orbit (200 by 20,000 miles (320 by 32,190 km)) passing the radiation belts will receive about 2,500 rem (25 Sv) per year.

[44] The astronauts had low exposure in the Van Allen belts due to the short period of time spent flying through them.

The total radiation received by the astronauts varied from mission-to-mission but was measured to be between 0.16 and 1.14 rads (1.6 and 11.4 mGy), much less than the standard of 5 rem (50 mSv)[c] per year set by the United States Atomic Energy Commission for people who work with radioactivity.

The inner belt is mainly composed of energetic protons produced from the decay of neutrons, which are themselves the result of cosmic ray collisions in the upper atmosphere.

The gap is caused by the VLF radio waves, which scatter particles in pitch angle, which adds new ions to the atmosphere.

Green of the Goddard Space Flight Center[citation needed] compared maps of lightning activity collected by the Microlab 1 spacecraft with data on radio waves in the radiation-belt gap from the IMAGE spacecraft; the results suggest that the radio waves are actually generated by lightning within Earth's atmosphere.

The generated radio waves strike the ionosphere at the correct angle to pass through only at high latitudes, where the lower ends of the gap approach the upper atmosphere.

Draining the charged particles from the Van Allen belts would open up new orbits for satellites and make travel safer for astronauts.