A theoretical framework of chorus wave excitation

TL;DR

This paper develops a comprehensive theoretical model for chorus wave excitation, capturing the evolution of wave spectra and electron distributions, and analytically deriving the chorus chirping rate with implications for plasma physics.

Contribution

It introduces a self-consistent framework that analytically derives chorus chirping rate and reconciles different interpretations within a unified theory.

Findings

Derived the chorus chirping rate expression analytically.

Reconciled various interpretations of chorus chirping.

Linked chorus phenomena to plasma physics and laser physics analogies.

Abstract

We propose a self-consistent theoretical framework of chorus wave excitation, which describes the evolution of the whistler fluctuation spectrum as well as the supra-thermal electron distribution function. The renormalized hot electron response is cast in the form of a Dyson-like equation, which then leads to evolution equations for nonlinear fluctuation growth and frequency shift. This approach allows us to analytically derive for the first time exactly the same expression for the chorus chirping rate originally proposed by Vomvoridis et al.,1982. Chorus chirping is shown to correspond to maximization of wave particle power exchange, where each individual wave belonging to the whistler wave packet is characterized by small nonlinear frequency shift. We also show that different interpretations of chorus chirping proposed in published literature have a consistent reconciliation within the present theoretical framework, which further illuminates the analogy with similar phenomena in fusion plasmas and free electron laser physics.