  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.
