Nonlinear bounce resonance interaction between equatorial noises and equatorially mirroring electrons in the magnetosphere

Abstract:

Equatorial noise, also known as fast magnetosonic waves or ion Bernstein mode waves, are electromagnetic emissions confined within a few degrees of the equator, occurring above the proton gyrofrequency and below the lower hybrid resonance frequency typically a few Hz to several hundreds Hz. It has been shown that these waves undergo Landau resonance interaction responsible for electron acceleration, and additional transit-time scattering because of spatial confinement near the equator. Furthermore, magnetosonic waves can also resonate with bounce motion of energetic electrons including those of pitch angle 90 degrees. We will characterize the effect of bounce resonances and discuss the consequence of bounce resonance. This is especially important on dynamics of equatorially mirroring energetic electrons, which poses an interesting scientific problem because they generally cannot gyro-resonate with any known plasma waves and hence cannot be scattered down to lower pitch angles. Nonlinear bounce scattering of equatorially mirroring electrons will be discussed, and its relation to the formation of butterfly distribution will be presented.