Strong Diffusion of Energetic Electrons by Equatorial Chorus Waves in the Midnight‐to‐Dawn Sector

Abstract

Drastic variations of radiation‐belt/ring current electrons are the result of competing processes of acceleration, transport, and loss. For subrelativistic energetic electrons (10–100 keV), one of the promising loss mechanisms is precipitation into the atmosphere due to pitch angle scattering by whistler mode chorus waves. The efficiency of the scattering has yet to be quantified by direct observations, however. Using in situ measurements by the ERG (Arase) spacecraft in the midnight‐to‐dawn sector at and around the magnetic equator, we demonstrate that the full filling of energetic electron loss cones occurs commonly, associated with typical‐amplitude (greater than 50 pT) chorus waves. The spatial distribution of the loss cone filling indicates that the efficient scattering is limited to |MLAT|< 10°.

Global Survey of Plasma Sheet Electron Precipitation due to Whistler Mode Chorus Waves in Earth's Magnetosphere

“…The electron scattering at 2.9 keV is mostly caused by upper band chorus, and the electron scatterings at 9.3 and 38 keV are mostly caused by LBC. Kasahara et al (2019) examined the energy profiles of the occurrence rates of strong diffusion above several keV, which is roughly consistent with the trend of electron scattering rate at 9.3 and 38 keV due to LBC waves.…”

Statistical Study of Approaching Strong Diffusion of Low‐Energy Electrons by Chorus and ECH Waves Based on In Situ Observations

“…To remove the dataset possibly related to the plasma sheet phenomena, we discarded the dataset if the angle between the background magnetic field and the model dipole field was >30° (cf., S. Kasahara et al, 2019). Moreover, we only used the dataset obtained outside the plasmapause (L* > 4 and the electron density <30 cm −3 ) to exclude the contribution from plasmaspheric hiss.…”

Spatial Evolution of Wave‐Particle Interaction Region Deduced From Flash‐Type Auroras and Chorus‐Ray Tracing

“…Kasahara et al. (2019) reported that the full filling of the loss cones of energetic electrons associated with chorus waves is commonly seen in in‐situ observations. Thus, the positive correlation suggests that the chorus wave growth saturates and/or reaches a strong diffusion limit due to the intense amplitude (Kennel, 1969).…”