Magnetic Reconnection on the Day Side of the Earth: Electron Acceleration and Electric Fields in the Electron Diffusion Region

This dissertation focuses on magnetic reconnection located on the day side of Earth's magnetosphere at the electron scale. Observations by the National Aeronautics and Space Administration's Magnetospheric Multiscale Mission are used to better define and understand various aspects of the electron diffusion region.

The first study of this dissertation focuses on an event at a nonprimary electron diffusion region where the motion of the spacecraft pass through the X-line in a sequential fashion that is optimal for detailed multi-spacecraft evaluation. By utilizing velocity distribution functions and corresponding energy spectrum coupled with readings of the normal electric field (EN), acceleration of the magnetosheath electrons crossing the X-line into the magnetopause is quantified for the first time.

The second study of the dissertation focuses on the reconnection electric field and normalized reconnection rates for fourteen reconnection events on the day side of the Earth's magnetosphere. Because the reconnection electric field component is much smaller than the other components, special care is taken to eliminate contamination by the larger components. This process is used for all 47 spacecraft that pass through electron diffusion regions in these events. We find that normalized reconnection rates vary greatly within very small temporal and spatial scales. No dependence between local or solar-wind parameters and the normalized reconnection rate is found, but there is a positive correlation between the unnormalized reconnection electric field and the solar-wind dynamic pressure in the magnetosheath. When summed over all spacecraft in these events, we find an average normalized reconnection rate of 0.15, which agrees with theoretical predictions.

In addition to this manuscript, supplementary material in the form of an Excel spreadsheet will be included that provides additional data pertaining to Chapter 3. This data set provides a range of physical properties and calculations acquired at each spacecraft on the fourteen dayside events studied, that were not included in the main text.