Date of Award

Spring 5-2017

Access Type

Thesis - Open Access

Degree Name

Master of Science in Engineering Physics

Department

Physical Sciences

Committee Chair

Katariina Nykyri

First Committee Member

Anatoly V. Streltsov

Second Committee Member

Kshitija Deshpande

Abstract

We present a case study of the 25 December 2015 substorm which occurred between 08:15 and 08:45 Universal Time. During this interval, fast particle flows and field geometry consistent with magnetic reconnection were detected in the mid-tail region. An ejected plasmoid was observed by the lunar-orbiting Acceleration, Reconnection, Turbulence and Electrodynamics of Moon’s Interaction with the Sun (ARTEMIS) probes and corresponding dipolarization signature was observed by the Time History of Events and Macroscale Interactions During Substorms (THEMIS) spacecraft earthward of the reconnection site, which was determined to be approximately -33 RE. Ground signatures indicative of substorm activity were also observed by the THEMIS ground-based observatories during this interval. Prior to the substorm, none of the solar-wind monitoring missions (Geotail, OMNI, ACE) observed a significant southward Bz which could have initiated the event. The Magnetospheric Multiscale (MMS) spacecraft, which were in the dayside magnetosheath, detected a strong pulse in Bz, with a minimum near -35 nT, at ∼08:05 UT, consistent with the time delay required for propagation from the magnetosheath to the mid-tail. We propose that this pulse is either a small-scale structure in the solar wind, the result of a kinetic shock process due to a solar wind discontinuity hitting the bow shock, or a flux-transfer event at the magnetopause and, further, that this strong southward component of Bz in the magnetosheath is associated with the trigger of the observed substorm. We simulate the entire magnetosphere in maximum detail for this event using the Space Weather Modeling Framework/Block Adaptive Tree Solar-wind Roe Upwind Scheme (SWMF/BATS-R-US) model from NASA’s Community Coordinated Modeling Center (CCMC) with a special, high resolution grid. The results of this work will be highly relevant to future solar wind observation missions, global-scale magnetohydrodynamic models, and the ongoing effort to understand how processes at lunar distances in the tail couple to the rest of the near-Earth space environment.

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