Resonant Absorption as Mode Conversion? II. Temporal Ray Bundle

TL;DR

This paper investigates how a fast-wave pulse in an inhomogeneous plasma partially reflects and partially converts to an Alfven wave at the resonance layer, with exact absorption coefficients derived.

Contribution

It provides a precise calculation of the absorption and mode conversion of a wave pulse in plasma, extending previous work with a detailed analysis of the temporal ray bundle.

Findings

Partial reflection and tunneling of the wave pulse at the resonance layer

Exact absorption coefficient is independent of frequency and pulse width

Mode conversion efficiency is characterized by a tabulated function

Abstract

A fast-wave pulse in a simple, cold, inhomogeneous MHD model plasma is constructed by Fourier superposition over frequency of harmonic waves that are singular at their respective Alfven resonances. The pulse partially reflects before reaching the resonance layer, but also partially tunnels through to it to mode convert to an Alfven wave. The exact absorption/conversion coefficient for the pulse is shown to be given precisely by a function of transverse wavenumber tabulated in Paper I of this sequence, and to be independent of frequency and pulse width.