Vlasov Simulation of Coherent Chorus Wave Emission in the Earth’s Magnetosphere

The whistler-mode chorus is a distinctive electromagnetic emission featuring a frequency chirping. It arises from the nonlinear interaction between resonant electrons and traveling whistler packets inside the Earth's magnetosphere. In this research, we have proposed a novel Hamiltonian theory and developed a corresponding Vlasov simulation code to study the excitation of coherent chorus waves in weakly inhomogeneous magnetic fields. The onset of chorus wave is simulated with different initial conditions and narrow/wide banded excitation source. The formation and evolution of electron phase-space trapped holes are traced, and the accompanying frequency chirping of chorus waves is recovered.  Notably, we found a new chorus wave generation process when the excitation source and initial wave spectrum are extremely narrow-banded. These excited waves follow a completely novel dispersion relationship, that differs significantly from that of the linear whistler waves. This study offers a fresh perspective on the nonlinear dynamics of chorus waves and provides important guidance for further research on the behavior of chorus waves across wide parameter ranges.