Theoretical and numerical studies of density modulated whistlers

Abstract

[1] Recently, observations from laboratory experiments, which are relevant to space observations as well, have conclusively revealed the amplitude modulation of whistlers by low-frequency perturbations. Our objective here is to present theoretical and simulation studies of amplitude modulated whistler packets on account of their interaction with background low-frequency density perturbations that are reinforced by the whistler ponderomotive force. Specifically, we show that nonlinear interactions between whistlers and finite amplitude density perturbations are governed by a nonlinear Schrödinger equation for the modulated whistlers, and a set of equations for arbitrary large amplitude density perturbations in the presence of the whistler ponderomotive force. The governing equations are solved numerically to show the existence of large scale density perturbations that are self-consistently created by localized modulated whistler wavepackets. Our numerical results are found to be in good agreement with experimental results, as well as have relevance to observations from magnetized space plasmas.

Exact theory for localized envelope modulated electrostatic wavepackets in space and dusty plasmas

“…whistler) waves (Kostrov, 2003). Recent numerical simulations of electron cyclotron waves (Eliasson and Shukla, 2004) (as well as earlier ones, by Hasegawa, 1970Hasegawa, , 1972) also predict such a behaviour.…”

On the transition between the Weibel and the whistler instabilities

“…In Refs. 20 and 21 it was later shown that these ponderomotive forces are reinforced due to the interaction of the whistler packets with the background low density perturbations 20 . In addition to the low density perturbations observed in our simulations (see Fig.10), the formation of wave packets of the perturbed magnetic field are also evident (see Fig.11, left frame).…”

Chorus waves and spacecraft potential fluctuations: Evidence for wave‐enhanced photoelectron escape

“…The amplitude and spatial distribution of chorus waves can be strongly influenced by ambient plasma density fluctuations through ducting [e.g., Koons 1989, and references therein] or modulated growth rates [Li et al, 2011]. Also, correlations between chorus wave amplitude and density structure may be expected if the waves modify the plasma density through ponderomotive interactions [e.g., Eliasson and Shukla, 2004] or if nonlinear sheath rectification effects are present [Boehm et al, 1994]. In situ observations have correlated large-scale (hundreds of kilometers) density fluctuations with enhanced chorus wave power [Scarf and Chappell, 1973;Koons, 1989].…”