Possible Global Generation Region of Nonlinear Whistler-Mode Chorus Emission Waves at Mercury

Chorus waves are a kind of intense electromagnetic emission wave in magnetized planets and can play important roles in the kinetic electron dynamics in planetary magnetospheres. Rapid changes of the ring electron current belt in Mercury's magnetosphere and the contribution of chorus waves have remained long-standing scientific issues from the first Mercury flyby observations by Mariner 10 in 1970s because of the small size of the magnetosphere. Based on theoretical analyses and simulations successfully reconstructing Earth's chorus wave properties, we report on possible generation regions of chorus waves in Mercury's magnetosphere. The theoretical analysis for low-temperature-anisotropy electrons shows a clear asymmetric day-night spatial distribution of the possible chorus generation region because of the difference in the nonlinear convective wave growth along the magnetic field lines. Simulation results show a rapid enhancement of the ring electron current belt by resonant interactions with repetitive chorus waves. Our study suggests that energetic electrons in Mercury's magnetosphere can be enhanced locally by nonlinear chorus wave-particle interactions. Possible global distribution of chorus waves at Mercury was estimated based on a nonlinear wave growth theory Nonlinear chorus waves at Mercury can show a clear day-night asymmetric distribution due to differences in convective growth Energetic electrons can evolve to a pancake-like pitch angle distribution in Mercury's ring electron current belt by chorus waves