Energization of electrons to relativistic energies and the dynamics of 
the plasmasphere: Case studies of recent events

S.G. Kanekal, D.N. Baker, J.B. Blake, J. Goldstein


The energization of electrons to relativistic energies in the outer
radiation belts (Van Allen belts) is not yet fully understood. The
primary causes, however, have long been known to be increased solar
wind speeds and the southward turning of the interplanetary magnetic
field. The radiation belts are extremely dynamic with flux increases of
over several orders of magnitude occuring within a few days.

Several models have been proposed to explain the physics of electron
energizatiom in the magnetosphere. These models may be be broadly
classified into two types. The first class of models are those with
in-situ wave particle interactions being the dominant source of
particle energization as well as loss due to pitch angle scattering. A
second class of models are those with the dominant mechanism beig one
of particle transport. Here too, the radial diffusion of particles may
be enhanced due to wave particle interactions.

It is well known that the boundary of the plasmasphere, i.e., the
plasmapause is a region where intense whistler waves can persist. These
waves which are confined and trapped [1] in the plasmasphere pitch
angle scatter electrons and lead to electron loss. At the same time
they can stochastically energize electrons to MeV energies [2]. Other
types of waves such as ULF waves are also affected the dynamics of the
plasmapause and are also capable of electron energization.

In this paper we report on the location and appearence of relativistic
electron flux increases and correlate them with plasmapause location
for select sample of events. Relativistic electron data are provided by
instruments onboard SAMPEX and POLAR. The IMAGE satellite provide a
global picture of the plasmapause location and is ideal for
determining the dynamics of the plasampause.

[1] D.N.Baker, et al., Nature 432, 878-881, 2004,
doi:10.1038/nature03116
[2] R.B.Horne and Thorne,R.M., GRL, Vol. 30, No. 10, 1527,
doi:10.1029/2003GL016973, 2003

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Presented at the 28th URSI General Assembly, New Delhi, India, 
23 - 29 October, 2005