The global distribution, energy source, and scattering effects of magnetosphic waves in the Earth's inner magnetosphere
The global distribution, energy source, and scattering effects of magnetosphic waves in the Earth's inner magnetosphere
Previously Published Material: Besides our new results first reported in this presentation, the previous findings in the following papers will be cited: Global distribution of equatorial magnetosonic waves observed by THEMIS, by Ma et al., Geophysical Research Letters, 2013; Magnetosonic wave excitation by ion ring distributions in the Earth's inner magnetosphere, by Ma et al., Journal of Geophysical Research, 2014; The trapping of equatorial magnetosonic waves in the Earth's outer plasmasphere, by Ma et al., Geophysical Research Letters, 2014.
Abstract ID#: 35319
English Abstract:
Equatorial magnetosonic waves are highly oblique whistler-mode electromagnetic emissions between the proton gyrofrequency and the lower hybrid resonant frequency, widely distributed in the Earth's inner magnetosphere, and may have potentially important effects in particle scattering in the radiation belts. Our global survey of magnetosonic waves using THEMIS fff data products has shown that the most intense magnetosonic waves are distributed on the dawn-noon sectors, with maximum root-mean-square averaged wave amplitudes ~50 pT and occurrence rates ~20%. Our instability analysis on a typical magnetosonic wave event has demonstrated that the unstable ion ring distributions could provide the free energy for the wave excitation outside the plasmapause or in the outer region of the plasmasphere. Although magnetosonic waves cannot be excited deep inside the plasmapause, the locally observed waves can be originated from the outer region and stay trapped in the plasmasphere, which is confirmed by our analysis on the wave perpendicular propagation. The magnetosonic waves can cause electron pitch angle and energy scattering via Landau resonance and transit time effects, and we further investigate their general influences on energetic electrons in the Earth's inner magnetosphere.