Pitch-Angle Scattering of Inner Magnetospheric Electrons Caused by ECH Waves Obtained With the Arase Satellite

Electrostatic electron cyclotron harmonic (ECH) waves are generally excited in the magnetic equator region, in the sector from nightside to dayside during geomagnetically active conditions, and cause the pitch angle scattering by cyclotron resonance. The scattered electrons precipitate into the Earth's atmosphere and cause auroral emission. However, there is no observational evidence that ECH waves actually scatter electrons into the loss cone in the magnetosphere. In this study, from simultaneous wave and particle observation data obtained by the Arase satellite equipped with a high-pitch angular resolution electron analyzer, we present evidence that the ECH wave intensity near the magnetic equator is correlated with an electron flux inside the loss cone with an energy of about 5 keV. The simulation suggests that this electron flux contributes to the auroral emission at 557.7 nm with an intensity of about 200 R.