Van Allen Belts Variability (IMAGE)
Caption
1. The traditional idea of the radiation belts includes a larger, more dynamic outer belt and a smaller, more stable inner belt with an empty slot region separating the two. However, a new study based on data from NASA's Van Allen Probes shows that all three regions--the inner belt, slot region, and outer belt -- can appear differently depending on the energy of electrons considered and general conditions in the magnetosphere.
2. At the highest electron energies measured -- above 1 MeV -- researchers saw electrons in the outer belt only.
3. The radiation belts look much different at the lowest electron energy levels measured, about 0.1 MeV. Here, the inner belt is much larger than in the traditional picture, expanding into the region that has long been considered part of the empty slot region. The outer belt is diminished and doesn't expand as far in these lower electron energies.
4. During geomagnetic storms, the empty region between the two belts can fill in completely with lower-energy electrons. Traditionally, scientists thought this slot region filled in only during the most extreme geomagnetic storms happening about once every ten years. However, new data shows it's not uncommon for lower-energy electrons -- up to 0.8 MeV -- to fill this space during almost all geomagnetic storms.
Credit
NASA Goddard/Duberstein
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