Rapid local acceleration of relativistic radiation-belt electrons by magnetospheric chorus

Abstract

Recent analysis of satellite data obtained during the 9 October 2012 geomagnetic storm identified the development of peaks in electron phase space density, which are compelling evidence for local electron acceleration in the heart of the outer radiation belt, but are inconsistent with acceleration by inward radial diffusive transport. However, the precise physical mechanism responsible for the acceleration on 9 October was not identified. Previous modelling has indicated that a magnetospheric electromagnetic emission known as chorus could be a potential candidate for local electron acceleration, but a definitive resolution of the importance of chorus for radiation-belt acceleration was not possible because of limitations in the energy range and resolution of previous electron observations and the lack of a dynamic global wave model. Here we report high-resolution electron observations obtained during the 9 October storm and demonstrate, using a two-dimensional simulation performed with a recently developed time-varying data-driven model, that chorus scattering explains the temporal evolution of both the energy and angular distribution of the observed relativistic electron flux increase. Our detailed modelling demonstrates the remarkable efficiency of wave acceleration in the Earth's outer radiation belt, and the results presented have potential application to Jupiter, Saturn and other magnetized astrophysical objects.

Probabilistic approach to nonlinear wave-particle resonant interaction

“…This is a fundamental process, responsible for many phenomena in space and laboratory plasmas. One of the brightest examples is electron acceleration in radiation belts, which results in aurora formation [1,2] and represents a real hazard for artificial satellites in activity [3]. Assuming that the wave spectrum is wide enough and the wave intensity is sufficiently low, one can model the wave-particle resonant interactions using quasi-linear theory [4][5][6][7] generalized for systems with inhomogeneous magnetic field and background plasma [8,9].…”

Theoretical analysis on lower band cascade as a mechanism for multiband chorus in the Earth’s magnetosphere

“…[1][2][3][4][5] These waves are believed to be a dominant source of "killer electrons" (∼MeV) in Earth's magnetosphere, 3,5,6 which is a major threat to astronauts and operating satellites. Furthermore, they are also the primary contributor of strong diffuse auroral precipitation into the Earth's atmosphere, 2,7 resulting in enhanced chemical changes of the atmosphere.…”

Probability of relativistic electron trapping by parallel and oblique whistler-mode waves in Earth's radiation belts

“…37,40,42,58,64,67 Multiple spacecraft observations of intense emissions of parallel (relative to the background magnetic field) whistler-mode waves during geomagnetic storms and substorms 1,33,38 have led to the suggestion that these parallel waves could be responsible for almost all the recorded variations of electron fluxes. In addition, oblique wave damping due to Landau resonance with a dense population of suprathermal electrons 20,36 often sensibly decreases the amplitudes of oblique whistler-mode waves along their propagation.…”