7 Space Weather in the Inner Magnetosphere

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 18View Image from Li et al. (2001Jump To The Next Citation Point) 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.

View Image

Figure 18: The top panel shows the inner belt proton flux in red and the sunspot number in black. The bottom panel shows the relativistic electron distribution in the inner magnetosphere. Color coding shows the inner magnetosphere relativistic electron flux intensity as a function of time and L shell giving the equatorial distance from the Earth. The black curve overlaid shows the daily averages of the Dst index (scale on the right), used here as a measure of the ring current energetic ion flux with more negative values indicating larger ring current (from Li et al., 2001).
 7.1 Time-variable electromagnetic fields
 7.2 Storm-time ring current
 7.3 Changes in the cold plasmasphere
 7.4 Relativistic electron acceleration and losses

  Go to previous page Go up Go to next page