First Author: Roth, I.,

Co-Authors: M. Temerin, E. G. D. Reeves, M. Hudson, and J. B. Blake,

Title: Resonant Enhancement of the >1 Mev Electron flux due to Interaction with Whistler Waves,

Reference: AGU Fall Meeting, San Francisco, CA, 8-12 December, 1997.

Reference Type: Contributed Talk

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Abstract: 
\begin{abstract} Enhancement of energetic electron fluxes at L $\sim$ 4.5 were observed during geomagnetic storm intervals, as well as during quieter times following high speed solar wind stream arrival at 1 AU. Consecutive passes of GPS satellites showed an increasing flux of 1.6-3.5 MeV electrons over several hours, both for the January 10-11, 1997$^1$ and the November 23-24, 1993$^2$ storm intervals. GPS data shows that increase in the flux of $<$ 1 MeV electrons precedes increase in the $>$ 1 MeV flux at L=4.5 for the January event, without significant flux increase initially at higher L values$^1$. This observation, and others by HEO spacecraft suggest that a local heating mechanism may be operative$^2$. We conjecture that the ubiquitous, sufficiently intense, obliquely propagating whistler waves, interact with electrons which bounce along the geomagnetic field 1ines. The large changes of the gyrofrequency along the electron trajectory and its large velocity allows it to resonantly interact with multiple harmonics of the whistler wave. We integrate the electron equation of motion in its full six-dimensional phase space and follow the nonadiabatic changes whenever an electron enters a resonance along its bounce trajectory. The resonant interaction is depicted in a Poincare-like diagram with two quantities plotted whenever the electron satisfies the resonance condition. We observe an effective diffusion in the first adiabatic invariant over several tens of electron bounces. The timescale of this process is often the order of minutes, many orders of magnitude smaller than the standard L-diffusion time scale. $^1$Reeves et al., IAGA Abstracts, Uppsala, Sweden p. 368, 1997 $^2$Li et al., JGR, 102, 14123, 1997.