Computational study of whistler-mode wave excitation in the Earth's inner magnetosphere

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Abstract
Whistler-mode waves play an important role in electron dynamics within planetary magnetospheres and are ubiquitously observed across a wide range of plasma environments. In Earth's inner magnetosphere, they are commonly classified into incoherent whistler, chorus, and hiss based on their spectral characteristics. This study presents a computational investigation under typical magnetospheric conditions to examine how plasma parameters determine the excitation of different whistler-mode waves. Under low-density conditions outside the plasmasphere, the parameter regimes leading to incoherent whistler, discrete-element chorus, and hiss-like chorus are identified. Peak wave amplitude is quantified for each simulation case, and an empirical relation is established to describe its dependence on hot electron number density and temperature anisotropy. Incoherent whistler waves are driven by linear instabilities of hot electrons, whereas chorus waves arise through nonlinear wave–particle interactions. The growth rates of chorus waves are quantified along the wave packet evolution and are consistent with theoretical predictions. Under high-density conditions within the plasmasphere or plume regions, hiss waves are preferentially generated. This study delineates the parameter regimes for simulating various whistler-mode waves and contributes to a deeper understanding of wave–particle interactions.
Funding Information
  • National Aeronautics and Space Administration (80NSSC24K0174)
  • NSF (AGS-2612002)

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