Whistler Mode Chirped-Solitons as the Building Blocks of Chorus

Whistler mode chorus is a powerful electromagnetic emission observed in the outer radiation belts of the Earth that is an important driver of the dynamics of energetic electrons through resonant wave-particle interactions. Chorus waves are characteristically quasi-coherent and are observed as bursts of wave power called chorus elements with frequencies in the VLF range that can change on time scales of the order of tens of wave periods. Chorus elements are further subdivided into sub-elements (or sub-packets) that are characterized by a peak in the wave amplitude. We show using Bayesian spectral analysis techniques that the most probable model for the sub-elements, among the models considered, that explains the data are chirped soliton's which are solutions to the Ginzburg-Landau equation. We derive a Ginzburg-Landau equation that is applicable to whistler mode chorus and analyze analytical and numerical solutions for chirped solitons. The data and theory suggests that these chirped soliton solutions form the building blocks of chorus elements. Having an accurate model of whistler mode chorus can provide accurate models of the effects of chorus on energetic electrons.