Parametric Study of Rising-Tone Chorus Wave Excitation in the Earth’s Inner Magnetosphere

Whistler-mode chorus waves are electromagnetic waves commonly observed in the Earth’s inner magnetosphere, playing a crucial role in driving pulsating auroras. Theoretical studies suggest that the excitation of chorus waves replies on nonlinear wave-particle interactions, requiring the wave amplitude to exceed a certain threshold for nonlinear processes to occur. However, this prediction still needs validation from numerical simulations. In this study, we perform a parametric investigation on rising-tone chorus wave excitation using one-dimensional simulations in the dipole fields. The dependence of wave amplitude on the number density and temperature anisotropy of energetic electrons has been quantified. It is found that nonlinear wave growth occurs only within a narrow parameter range, where the wave amplitude is between the threshold and optimum amplitudes, which represent the lower and upper limits for nonlinear wave-particle interactions, respectively.This study provides significant insights into the quantification of chorus wave excitation under different parameters, contributing to a more comprehensive understanding of nonlinear wave-particle interactions.