Can ECH Wave Scattering Explain the Unaccounted Electron Loss During the 17 March 2013 Geomagnetic Storm?

Abstract The interaction of electrons with electrostatic electron cyclotron harmonic (ECH) waves in the Earth's magnetosphere can lead to the scattering of plasma sheet electrons into the atmospheric loss cone, affecting the evolution of electron phase space density. Previous studies have shown that ECH waves are capable of efficiently scattering electrons with energies ranging from several hundred electronvolts to a few kiloelectronvolts, depending on the wave properties. At the same time, recent results indicate that ring current models overestimate the electron flux of 10–50 keV during storm time, implying the existence of a missing nightside loss process. Since the scattering rates due to wave‐particle interactions with ECH waves, which are currently not incorporated in quasi‐linear studies of ring current dynamics, increase with increasing geomagnetic activity, ECH waves are a potential candidate to explain part of the missing loss process. In this study, we evaluate the efficiency of ECH wave scattering for a wave event that occurred during the geomagnetic storm on 17 March 2013, by calculating quasi‐linear bounce‐averaged scattering rates. The resulting lifetimes are incorporated into simulations conducted using the 4‐dimensional Versatile Electron Radiation Belt (VERB‐4D) code. The results demonstrate that ECH waves during this event can scatter electrons over a wide range of energies up to several keV, but the resulting lifetimes are too long to significantly alter the resulting pitch angle distribution. Consequently, we find no evidence in support of the hypothesis that direct scattering due to ECH waves contributes to the missing loss process.