Bibliography

Nonlinear Electrostatic Steepening of Whistler Waves: The Guiding Factors and Dynamics in Inhomogeneous Systems

Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The efficiency of wave-particle resonant interactions is defined by whistler wave properties which have been described by the approximation of plane linear waves propagating through the cold plasma of the inner magnetosphere. However, recent observations of extremely high-amplitude whistlers suggest the importance of nonlinear wave-particle interactions for the dynamics of the outer radiation belt. Oblique chorus waves observed in the inner magnetosphere often exhibit drastically nonsinusoidal (with significant power in the higher harmonics) waveforms of the parallel electric field, presumably due to the feedback from hot resonant electrons. We have considered the nature and properties of such nonlinear whistler waves observed by the Van Allen Probes and Time History of Events and Macroscale Interactions define during Substorms in the inner magnetosphere, and we show that the significant enhancement of the wave electrostatic component can result from whistler wave coupling with the beam-driven electrostatic mode through the resonant interaction with hot electron beams. Being modulated by a whistler wave, the electron beam generates a driven electrostatic mode significantly enhancing the parallel electric field of the initial whistler wave. We confirm this mechanism using a self-consistent particle-in-cell simulation. The nonlinear electrostatic component manifests properties of the beam-driven electron acoustic mode and can be responsible for effective electron acceleration in the inhomogeneous magnetic field.

Agapitov, O.; Drake, J.; Vasko, I.; Mozer, F.; Artemyev, A.; Krasnoselskikh, V.; Angelopoulos, V.; Wygant, J.; Reeves, G.;

Published by: Geophysical Research Letters      Published on: 03/2018

YEAR: 2018     DOI: 10.1002/2017GL076957

Electron acceleration; electron acoustic waves; induced scattering; nonlinear wave-particle interactions; Van Allen Probes; wave steepening; Whistler waves

Generation of nonlinear Electric Field Bursts in the outer radiation belt through the parametric decay of whistler waves

Huge numbers of different non-linear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on the Van Allen Probes. Some of them are associated with whistler waves. Such TDS often emerge on the forward edges of the whistler wave packets and form chains. The parametric decay of a whistler wave into a whistler wave propagating in the opposite direction and an electron acoustic wave is studied experimentally as well as analytically, using Van Allen Probes data. The resulting electron acoustic wave is considered to be the source of electron scale TDS. The measured parameters of the three waves (two whistlers and the electron acoustic wave) are in a good agreement with an assumption of their parametric interaction: ω0 = ω1 + ω2 and inline image. The bi-coherence analysis shows the non-linear nature of the observed electron-acoustic waves as well as the whistler wave and electron acoustic wave phase relation. The estimated decay instability growth rate shows that the process of three wave interaction can develop in a characteristic time smaller than one second, thus the process is rapid enough to explain the observations. This induced parametric interaction can be one of the mechanisms for quasi-periodic TDS generation in the outer Van Allen radiation belt.

Agapitov, O.; Krasnoselskikh, V.; Mozer, F.; Artemyev, A.; Volokitin, A.;

Published by: Geophysical Research Letters      Published on: 05/2015

YEAR: 2015     DOI: 10.1002/2015GL064145

electron acoustic waves; nonlinear structure formation; parametric decay of whistlers; Van Allen Probes