Date of Award
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Space Science
Committee Chair
Qiang Hu
Committee Member
Gary Zank
Committee Member
Lingling Zhao
Committee Member
Jakobus le Roux
Committee Member
Laxman Adhikari
Research Advisor
Qiang Hu
Subject(s)
Interplanetary magnetic fields, Shock waves, Solar wind, Magnetosphere
Abstract
This work identifies and characterizes magnetic structures in the solar wind and magnetosheath across the Earth’s bow shock. I investigate the differences between the properties of small-scale flux rope (SFR) structures immediately upstream and downstream of the bow shock by employing two data analysis methods: one based on wavelet transforms and the other based on the Grad-Shafranov (GS) detection and reconstruction techniques. 676 hours in the solar wind, and 1051 hours in the magnetosheath, of in situ magnetic field and plasma data from the Magnetospheric Multiscale (MMS) and Time History of Events and Macroscale Interactions during Substorms (THEMIS) missions were used to identify these coherent structures. I investigate the difference between the properties of the magnetic structures in different near-Earth regions. The magnetic structures with varying degrees of Alfvénicity are characterized in a systematic manner as they move across boundaries in near-Earth space. I identified thousands of SFR event intervals in each region, and established an inventory of events with high magnetic helicity. I report the parameters associated with the SFRs such as scale size, duration, and magnetic helicity density, and a direct comparison of the statistical properties of the structures from these two regions is performed. The GS-based method is extended to identify structures with significant remaining plasma flow aligned with the local magnetic field, and yielded a unique set of additional parameters that allowed us to evaluate the distributions of the Walén test slope, magnetic flux, and the orientation of the z-axes of the structures. In general, it is found that the distributions of various parameters follow power laws. The SFR structures seem to be compressed in the magnetosheath, as compared with their counterparts in the solar wind. A significant rotation in the z-axis defining the orientation of the structures is also seen across the bow shock. The implications for the elongation of the SFRs in the magnetosheath along one spatial dimension are also discussed.
Recommended Citation
Harvey, Rebecca, "Observational analysis of small-scale structures across the Earth’s bow shock" (2025). Dissertations. 460.
https://louis.uah.edu/uah-dissertations/460