Unraveling the Role of Electron Plateau Distributions in the Power Gap Formation of Chorus Waves: Van Allen Probes Observations

Abstract

AbstractThe power gap of chorus waves at ∼0.5fce has been discovered for decades, but its generation mechanism is still under debate. Previous studies have revealed that electron plateau distributions are vitally important for the gap formation. By analyzing over one‐year Van Allen Probes data, we have studied chorus waves with (banded events) and without a power gap (no‐gap events), and their correlations with the electron plateau distribution. Although there is no significant difference in the morphology of velocity distributions in banded and no‐gap events, banded chorus events are typically accompanied by a plateau component with about one order higher number density than no‐gap events. The plateau components can cause severe damping at ∼0.5fce through cyclotron resonance rather than Landau resonance, and the gap frequency is roughly determined by the bulk velocity of plateau components. Our study provides new observational constraints on the generation mechanisms of power gap.