Relativistic electrons in the radiation belt and Current sheet in the solar wind

First Oral Exam

Graduate Student: Zijin Zhang Supervisor: Vassilis Angelopoulos Committee Members: Marco Velli, Hao Cao, Anton Artemyev

Part 1: Relativistic electron flux decay and recovery: relative roles of EMIC waves, chorus waves, and electron injections

We examined a particular event on 17 April 2021 characterized by a series of strong electron and ion injections, significant electron precipitation driven by EMIC and chorus waves, and electron acceleration mainly attributable to chorus waves.
This case study is unique in the sense that strong EMIC and chorus wave-driven electron losses do not necessarily correspond to a simultaneous decrease of trapped electron fluxes. Sufficiently strong injections and chorus wave-driven electron acceleration in the presence of a sufficiently steep negative electron energy PSD gradient can balance such wave-driven losses.

Statistically study the conditions that lead to relativistic electron flux decay and recovery.
Understand the physical mechanisms that lead to the observed electron flux: strong diffusion or non-linear wave-particle interactions.

The normalized occurrence rate decreases with radial distance from the Sun, following a 1/𝑟 relationship in the outer heliosphere.
Normalized thickness and current density of discontinuities remain constant with radial distance (negligible change compared to their spread)
- Thickness => ion inertial length
Current density => Alfven velocity (current density)
Better alignment period has a slightly better agreement of the properties of the discontinuities (normalized thickness, current density, \(|\Delta \mathbf{B}/B|\) and rotation angle). \(B_N/B\) and in-plane rotation angle, however, are significantly different.

Understand the constant normalized thickness and current density of discontinuities with radial distance and change in the \(B_N/B\) and in-plane rotation angle.