Nonlinear Wave Processes in Earth's Radiation Belts
Abstract
Injection of energetic seed electrons from the plasma-sheet during substorms provides the conditions for the generation of whistler-mode chorus waves in the equatorial region of Earth's outer radiation belt. Chorus waves are instrumental in both accelerating electrons and inducing electron precipitation loss to the atmosphere. The generation of whistler-mode emissions comprises a linear stage followed by a nonlinear stage. In the linear stage the wave frequency is constant,and wave growth is driven by temperature anisotropy. In the nonlinear stage the wave frequency increases in time,resulting from nonlinear features including wave trapping and formation of a resonant current. The nonlinear evolution of wave frequency and amplitude at the equator are described by recently developed "chorus equations". We solve the chorus equations to determine how the nonlinear wave growth rate depends on the input parameters and the particle distribution function. In addition,we examine the spatio-temporal evolution of these waves during propagation away from the equator along a dipole field line,and,in particular,we analyze how the adiabatic variation of the particle distribution function off the equator contributes to wave saturation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMSM24A..06S
- Keywords:
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- 2774 MAGNETOSPHERIC PHYSICS / Radiation belts