Coherent interaction of magnetospheric particles with
large-scale disturbances
Processes affecting the dynamics of energetic particles in the inner
magnetosphere may be broadly categorized as either stochastic processes,
describing the individually-random dynamics of an ensemble of particles
interacting with a spectrum of magnetospheric waves; or coherent processes,
whereby the dynamics of the particles are collectively driven in one direction
in energy or space. Examples of coherent processes of particular importance in
the inner magnetosphere include the injection of particles from the plasmasheet
into the stable trapping region during substorms, and injections of
previously-trapped particles from high L values during impulsive events induced by shocks in the solar wind.
In this effort we investigate the results of
coherent interactions of energetic particles with large scale magnetospheric
disturbances , using analytic and MHD simulations of the global magnetosphere
combined with models based on a Fokker-Planck formalism of trapped particle dynamics.
The emphasis of this work is twofold: 1) How can
we characterize bulk particle dynamics during injection events associated with
substorm dipolarization and shocks in the solar wind? and 2) What are the appropriate forms of the transport
coefficients needed to effectively model impulsive injections of trapped particles
in a Fokker-Planck formalism? Understanding the factors controlling access
will provide much needed insight into the seed populations of trapped electrons and
ions that undergo subsequent stochastic acceleration through interaction with ULF
and VLF waves. Developing the Fokker-Planck formalism will provide a framework
for efficiently including coherent processes in modeling efforts, without appealing
to computationally-expensive global simulations of impulsive or convective
magnetospheric events.
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