The nonlinear wave-particle and wave-wave interactions in the outer radiation belt

Abstract : Observations by the Van Allen Probes and THEMIS provide high-quality ELF/VLF measurements of wave electric field that revealed the new nonlinear electron scales features in the outer radiation. The process of chorus generation significantly modify the local electron distribution function leading to forming the field aligned electron flux. The parallel electric field component of whistler-mode waves provides trapping of hot electrons into the effective potential and in inhomogeneous systems such as the dipole-like geomagnetic field allow an efficient parallel acceleration up to ~20-200 keV eventually leading to bursty precipitation (observed as microbursts at ionospheric altitudes). The mechanisms that produce nonlinear electric field structures, including the nonlinear evolution of oblique whistler-mode waves due to electron trapping and the parametric interaction of whistler waves have been determined. Important nonlinear processes responsible for rapid particle acceleration or scattering, with a significant effect on the global dynamics of the outer radiation belt, are: generation of chorus waves and corresponding generation of field aligned electron flux; whistler-mode waves with a large parallel electrostatic component providing Landau trapping into the wave effective potential with rapid parallel acceleration and possible bursty precipitation; lower energy electron population and filed aligned beams provide the possibility for nonlinear wave-wave coupling of whistlers and generation of electron acoustic mode and localized electric field bursts; nonlinear wave-particle interactions with oblique whistlers influence the global dynamics of the electron distribution in the outer radiation belt leading to separate observations of intense very oblique and parallel chorus in the outer radiation belt.