One- and two-dimensional simulations of whistler mode waves in an anisotropic plasma
- Univ. of Sussex, Brighton (United Kingdom)
- Culham Lab., Oxfordshire (United Kingdom)
We present results from self-consistent, one- and two-dimensional, electromagnetic simulations of the electron whistler mode instability relevant to the near-Earth nightside plasma sheet region during geomagnetically disturbed times. Specifically, we study the evolution of energetic, anisotropic electron distributions that are injected into the nightside ring current region at geomagnetically disturbed times, the resulting growth of electron whistler mode waves, and subsequent electron pitch angle diffusion via electron whistler wave-particle interactions. Growth of whistler mode waves from an initial pitch angle anisotropy (T{perpendicular} {approx} 4T{parallel}) is studied in the strong pitch angle diffusion regime (defined as having scattering times much shorter than a typical electron bounce time in the near Earth`s dipolar field). The quasi-linear and subsequent nonlinear evolution of waves and the corresponding migration of electrons in velocity space is followed over timescales such that ion motion may be neglected. Our simulations contain wave frequencies and growth rates that are a significant fraction of the electron gyrofrequency and the simultaneous evolution of waves propagating both parallel and nonparallel to the ambient magnetic field direction. Effects due to these are not usually accounted for in applications of quasi-linear theory to the problem of electron whistler wave-particle interactions, so that our self-consistent simulations of the electron whistler instability provide an important insight into the applicability of quasi-linear theory to the velocity space diffusion of electrons due to electron whistler wave-particle interactions. We examine the dependence of whistler mode wave growth rates, nonlinear wave mode saturation, and pitch angle diffusion rates on the {beta} value of the hot electron species which contains the resonant population, and we compare the differences between results of one- and two-dimensional simulations.
- OSTI ID:
- 175835
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A9 Vol. 100; ISSN JGREA2; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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