Counter-Streaming Interaction between Fast Magnetosonic Wave and Radiation Belt Electrons

Fast magnetosonic(MS)waves have been suggested to be able to effectively accelerate radiation belt electrons.We present gyro-averaged test-particle simulations to investigate counter-streaming interaction between MS wave and radiation belt electrons.It is found that an MS wave can significantly scatter counter-streaming electrons through a non-resonant process.The corresponding energy diffusion coefficients for counter-streaming interaction are always comparable to those for co-streaming interaction,independent of wave normal angle.The pitch-angle and cross diffusion coefficients of counter-streaming interaction are much smaller than those of co-streaming interaction for small normal angles,while they become comparable for large normal angles.Moreover,the bounce-averaged diffusion coefficients exhibit quite different distribution from those for co-streaming or counter-streaming alone in the pitch-angle-energy space.These results suggest that the non-resonant effect associated with counter-streaming interaction is indispensable for the acceleration processes driven by an MS wave.

Normal-Angle Dependence of the Interaction between Radiation Belt Electrons and Fast Magnetosonic Waves

Fast magnetosonic(MS)waves have been suggested to contribute significantly to radiation belt electron dynamics via Landau resonance and transit time scattering.The corresponding quasi-linear diffusion coefficients in pitch angle,energy and particularly cross-pitch-angle-energy are calculated from the gyro-averaged test-particle simulations.It is found that the cross diffusion coefficient is an effective indicator to differentiate between the contributions of resonant and non-resonant mechanisms.Furthermore,the dependence of diffusion coefficients on the normal angle of MS waves are parametrically investigated.Numerical results show that the increasing normal angle can lead to the shrinking of the Landau resonance region and the expansion of the transit-time scattering region.With the increasing normal angle,the pitch angle diffusion coefficients decrease significantly(by about two orders of magnitude),while the other two diffusion coefficients have a relatively limited decrease(within one order of magnitude).For arbitrary normal angles,the magnitude of cross diffusion coefficients is comparable to the other diffusion coefficients,suggesting that the cross diffusion is indispensable in the kinetic simulation works.

Magnetoacoustic Waves in the Solar Stratified Atmosphere

The propagation of magnetoacoustic waves in the solar atmosphere consisting of the photosphere, chromosphere and corona has been studied numerically by time-dependent multi-dimensional magnetohydrodynamic (MHD) simulation. Pressure disturbances are introduced at the bottom of the chromosphere and at the bottom of the corona, respectively. The computational results show that incurred fast and slow MHD waves propagate away from the source of the disturbances. The fast MHD wave propagates as an expansive wave in the radial direction, while the slow one steepens and it may evolve into a slow shock. We suggest that the extreme ultraviolet imaging telescope wave observed by the SOHO and Moreton wave are a fast MHD wave propagating in the corona and in the chromosphere, respectively.