The quasi-dipolar inner magnetosphere extending roughly out to geostationary distance has a variable field structure caused by the competing effects of the internal dipole field, magnetotail current sheet, dayside magnetopause currents, and the ring current within the region itself. Furthermore, the inner magnetosphere hosts multiple plasma populations: the hot ion ring current in the tens to hundreds of keV energy range, the outer van Allen belt electrons with energies from 100 keV up to several MeV, and the cold plasmaspheric plasma (from a few eV to few hundred eV) originating from the ionosphere. Recent research results have emphasized how effectively all these seemingly distinct populations and their dynamics are coupled together (Meredith et al., 2006).
Relativistic electrons in the inner magnetosphere are a major hazard for Earth-orbiting spacecraft, and therefore prediction of the electron fluxes especially at geostationary orbit is one of the key targets for space weather applications. Figure 18 from Li et al. (2001) shows the long-term variation of the relativistic electrons in the outer van Allen belt color coded as a function of time and distance from the Earth (L giving roughly the distance from the Earth in the equatorial plane) and the Dst index which is assumed to reflect the intensity of the ring current carried by the energetic ions. It is evident that in the large scale, there is an association between the magnetic storm activity (Dst) and the relativistic electron fluxes. Note also that the electron fluxes are significantly lower and further away from the Earth during the solar minimum period in 1996 – 1997.
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