Author ORCID Identifier
0000-0002-0815-9855
Document Type
Dissertation
Date of Award
8-31-2026
Degree Name
Doctor of Philosophy in Applied Physics - (Ph.D.)
Department
Physics
First Advisor
Hyomin Kim
Second Advisor
Haimin Wang
Third Advisor
Lindsay Goodwin
Fourth Advisor
Xuejian Wu
Fifth Advisor
Lauren Blum
Abstract
Small-scale magnetic flux ropes (SMFRs) in the solar wind are examined to determine their properties in the near-Earth upstream region and their effects on geospace. Although SMFRs are observed frequently in the solar wind, their statistical behavior near Earth and their role in solar wind-magnetosphere-ionosphere coupling remain insufficiently constrained. In this dissertation, an automated Grad-Shafranov reconstruction technique is applied to magnetic field and plasma measurements from MMS and Wind, and ionospheric responses are investigated using geomagnetic indices and SuperDARN observations. During the survey period, MMS has an apogee of approximately 25-29 RE. This orbital configuration allows the near-Earth upstream solar wind to be examined immediately before it interacts with the Earth.
A total of 2,355 SMFRs is identified from MMS and 26,305 from Wind. The events occur under magnetic field and plasma conditions characteristic of quiet solar wind near 1 AU. Most event diameters are below 150 RE, and axial orientations are found to align preferentially with the Parker spiral. In the near-Earth upstream region sampled by MMS, SMFRs are distributed broadly rather than concentrated in a preferred spatial sector. Their occurrence rates remain approximately steady across solar cycles. Magnetic properties, including total magnetic flux, total axial magnetic flux, and total magnetic field magnitude, vary with solar-cycle phase, whereas geometric properties such as duration and diameter do not. Dynamic-pressure changes at event onset are generally small, with most values falling within ±1 nPa, indicating that SMFRs are not typically associated with strong compressive disturbances.
Two case studies further show that, in both cases, SMFRs are associated with long-lived, spatially stationary ionospheric vortices that persist for approximately 1.5 hours under weak solar-wind driving. The distinct internal magnetic topologies in the two cases produce contrasting large-scale coupling responses: southward-oriented structure enhances coupling, whereas northward-oriented structure suppresses it. These results indicate that the geospace effects of SMFRs are controlled primarily by internal magnetic topology rather than by dynamic-pressure forcing alone. The persistence of mesoscale vortices under contrasting coupling conditions suggests that localized ionospheric responses do not scale directly with global convection strength. These observations support topology-dependent responses predicted by global MHD simulations and link SMFRs directly to high-latitude electrodynamics.
Recommended Citation
Shin, Youra, "Solar wind - magnetosphere - ionosphere coupling processes through small-scale magnetic flux ropes" (2026). Dissertations. 1899.
https://digitalcommons.njit.edu/dissertations/1899
