Combined Scattering of Outer Radiation Belt Electrons by Simultaneously Occurring Chorus, Exohiss and Magnetosonic Waves

We report a typical event that magnetosonic (MS) waves, exohiss and two-band chorus waves occurred simultaneously on the dayside observed by Van Allen Probes on 25 December 2013. By combining calculations of electron diffusion coefficients and 2-D Fokker-Planck diffusion simulations, we quantitatively analyze the combined scattering effect of multiple waves to demonstrate that the net impact of combined scattering does not simply depend on the wave intensity dominance of various plasma waves. Although the observed MS waves are most intense among the three wave modes, the electron butterfly distribution is inhibited due to scattering by exohiss and chorus waves, and outer zone electrons are considerably accelerated due to the combined diffusion of MS and chorus waves. Exohiss induced electron scattering loss effect is overall small, possibly due to its weakest wave intensity. The simulated evolution of outer zone electron phase space density shows good agreement with the observations in terms of both electron acceleration and pitch angle distribution especially for energetic to sub-MeV electrons, strongly suggesting that competition and cooperation between resonant interactions with concurrently occurring magnetospheric waves needs to be carefully treated in modeling and comprehending the radiation belt electron dynamics.