[P-EM11] Dynamics of the Inner Magnetospheric System

[PEM11-14] Strong diffusion of energetic electrons by plasmaspheric hiss waves

*Shin Sugo¹, Satoshi Kasahara¹, Yoshizumi Miyoshi², Kunihiro Keika¹, Shoichiro Yokota³, Tomoaki Hori², Yoshiya Kasahara⁴, Shoya Matsuda⁴, Iku Shinohara⁵, Ayako Matsuoka⁶ (1.The University of Tokyo, 2.Nagoya University, 3.Osaka University, 4.Kanazawa University, 5.Japan Aerospace Exploration Agency/Institute of Space and Astronautical Science, 6.Kyoto University)

Keywords:plasmaspheric hiss, energetic electrons, pitch angle diffusion

Hiss waves play an important role in the loss of 10s-100s of keV electrons, leading to the formation of the slot region in the Earth radiation belt. The Van Allen Probes revealed the energy- and L-shell-dependent loss of energetic electrons around the slot region, and the energy dependence is consistent with the resonance energy with hiss waves. However, some models considering scattering by hiss waves and radial diffusion do not completely explain the lifetime of electrons due to the small pitch angle diffusion coefficient (D_αα<10^-5 /s ). On the other hand, a recent global model of pitch angle scattering showed that the strong diffusion occurs on the dayside plasmasphere by hiss waves (D_αα>10^-4 /s ). Nevertheless, direct observational evidence of the strong pitch angle scattering of energetic electrons by hiss waves has not yet been obtained due to a difficulty in resolving small loss cone near the magnetic equator, where the scattering occurs. We found that the loss cone is filled with substantial electron flux of ~10-100 keV in the plasmasphere by analyzing data from the MEP-e instrument with the high angular resolution onboard the ERG satellite. Furthermore, we revealed that the strength of the loss cone flux and hiss waves are correlated in some events.