Approximate analytical solutions for the trapped electron distribution due to quasi-linear diffusion by whistler mode waves
Résumé
The distribution of trapped energetic electrons inside the Earth’s radiation belts is the focus
of intense studies aiming at better describing the evolution of the space environment in the presence of
various disturbances induced by the solar wind or by an enhanced lightning activity. Such studies are
usually performed by means of comparisons with full numerical simulations solving the Fokker-Planck
quasi-linear diffusion equation for the particle distribution function. Here we present for the first time
approximate but realistic analytical solutions for the electron distribution, which are shown to be in good
agreement with exact numerical solutions in situations where resonant scattering of energetic electrons
by whistler mode hiss, lightning-generated or chorus waves, is the dominant process. Quiet time
distributions are well recovered, as well as the evolution of energized relativistic electron distributions
during disturbed geomagnetic conditions. It is further shown that careful comparisons between the
analytical solutions and measured distributions may allow to infer important bounce- and drift-averaged
wave characteristics (such as wave amplitude). It could also help to improve the global understanding of
underlying physical phenomena.
Domaines
Planète et Univers [physics]
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