Space Physics Seminar spring-2017

Magnetosonic waves: fascinating spectral structures and importance to radiation belt electron dynamics

The fast magnetosonic waves are fascinating because they exhibit many kinds of structures in spectrum. Despite the harmonic structures and the rising-tone structures, we report a new form of “zipper-like” magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra observed by multiple missions. The two discrete bands are distinct in frequency and intensity, however, they maintain the same periodicity which varies in space and time, suggesting a nonlinear excitation or modulation mechanism which still remains to be fully understood. Strong magnetosonic waves were observed in the same region and at the same time periods as the radiation belt electron butterfly distributions, and as the magnetosonic waves expand in space, the butterfly distributions extend to the same region. Our simulations successfully reproduced the formation of electron butterfly distributions, which result from parallel acceleration caused by Landau resonant interaction. Multi-case studies show that magnetosonic waves can create electron butterfly distributions at energies from ~100 keV to multi-MeV, in a wide spatial range (L=1.2-4.8) of the radiation belts.