Investigate the effect of bounce resonance between fast magnetosonic waves and energetic electrons

Abstract:

Equatorial noises are fast magnetosonic wave emissions that are nearly perpendicular propagating and confined near the geomagnetic equator within several degrees. We investigate the effect of bounce resonance between a fast magnetosonic wave and equatorially mirroring electrons using test particle simulation. Bounce resonance occurs when wave frequency matches multiple of electron bounce frequency. We find that the bounce resonance can lead to nonlinear oscillation of equatorially trapped electrons when wave frequency is near first few harmonics of electron bounce frequency. When in bounce resonance, the oscillation amplitude increases for larger wave amplitude, smaller wave normal angle, or larger plasma density. This oscillation is important for dynamics of equatorially mirroring electrons above 100 keV, because it can produce finite vz, which could enable gyro-resonance interaction with other waves such as whistler mode waves.