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Analytical Model of a Toroidal Mode Field Line Resonance and Its Drift-Resonant Interaction With Energetic Electrons
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DOI：10.1029/2025JA034496.png)
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Abstract
En 中文
Ultra-low-frequency (ULF) waves play a critical role in magnetospheric dynamics, yet their transient growth and resonant electron interactions remain poorly understood. We develop a first-principle model of toroidal mode field line resonances that captures wave growth, saturation, and phase mixing. The model reproduces magnetospheric multiscale (MMS) observations of a microinjection event (4 August 2016), explaining wavefield beat patterns as phase mixing signatures. Guiding-center test-particle simulations reveal two distinct drift-resonance types: Type A (energy-dispersive) and Type B (gradient-driven, non-dispersive) resonance islands. These structures trap energetic electrons, producing repetitive flux enhancements matching MMS energy-time spectrograms. Energy-dependent phase shifts align with the 90 degrees lag predicted by drift resonance theory. We demonstrate that local wave-particle interactions can generate microinjections without remote substorm injections, potentially resolving a long-standing ambiguity in magnetospheric physics. By bridging magnetohydrodynamic theory and spacecraft observations, we provide a framework for diagnosing ULF wave-electron coupling with direct implications for radiation belt modeling and space weather forecasting.
Keywords:
toroidal mode
drift-resonant interaction
Journal
J
IF:
2.9
Papers:
268
Citations:
0
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