Resonance broadening due to particle scattering and mode-coupling in the quasi-linear relaxation of electron beams

Abstract

Of particular interest for radio and hard X-ray diagnostics of accelerated electrons during solar flares is the understanding of the basic non-linear mechanisms regulating the relaxation of electron beams propagating in turbulent plasmas. In this work, it is shown that in addition to scattering of beam electrons, scattering of the beam-generated Langmuir waves via for instance mode-coupling, can also result in broadening of the wave-particle resonance. We obtain a resonance-broadened version of weak-turbulence theory with mode-coupling to ion-sound modes. Resonance broadening is presented here as a unified framework which can quantitatively account for the reduction and possible suppression of the beam instability due to background scattering of the beam electrons themselves or due to scattering of the beam-generated Langmuir waves in fluctuating plasmas. Resonance broadening being essentially equivalent to smoothing of the electron phase-space distribution, it is used to construct an intuitive physical picture for the stability of inverted populations of fast electrons that are commonly observed \emph{in-situ} to propagate in the solar-wind.

arXiv commentPublished in JGR

References in corpus (8)

• Measurement of the electric fluctuation spectrum of magnetohydrodynamic turbulence
• Stochastic Acceleration by Turbulence
• Parallel electric field generation by Alfven wave turbulence
• Wave-particle interactions in non-uniform plasma and the interpretation of Hard X-ray spectra in solar flares
• Density fluctuations and the acceleration of electrons by beam-generated Langmuir waves in the solar corona
• Turbulent cross-field transport of non-thermal electrons in coronal loops: theory and observations
• Gyrofluid description of Alfvenic turbulence and its parallel electric field
• Canonical Hamiltonians for waves in inhomogeneous media

Cited by in corpus (7)

• Langmuir Wave Electric Fields Induced by Electron Beams in the Heliosphere
• A comparison of weak-turbulence and PIC simulations of weak electron-beam plasma interaction
• Harmonic radio emission in randomly inhomogeneous plasma
• The collisional resonance function in discrete-resonance quasilinear plasma systems
• A Fokker-Planck Framework for Studying the Diffusion of Radio Burst Waves in the Solar Corona
• Stopping Frequency of Type III Solar Radio Bursts in Expanding Magnetic Flux Tubes
• Shear Viscosity of Turbulent Chiral Plasma