Statistical Study of Whistler-mode Waves during Substorm Injections

Abstract:

Trapped particles in the magnetosphere can be lost, transported in the system or energized; and geomagnetic events can be considered as drivers of any of these processes. Loss of these electrons into the atmosphere or “precipitation” is one of the major routes for loss. Precipitated electrons deposit energy into the atmosphere and affect the ionization rate in ionosphere. One type of event that is associated with the precipitation is substorm injections. Energetic Electron Precipitation (EEP) associated with substorm injections typically occurs when magnetospheric waves, particularly whistler-mode waves, resonantly interact with electrons to affect their equatorial pitch angle. This can be considered as a diffusion process that scatters particles into the loss cone.

In this study, we investigate whistler-mode wave generation in conjunction with electron injections using in-situ wave measurements by the Themis mission. We particularly characterize the chorus waves in the substorm injection region to constrain the typical chorus wave behavior associated with electron injection.