Author ORCID Identifier
Date of Award
Spring 6-8-2026
Document Type
Thesis (Undergraduate)
Department
Physics and Astronomy
First Advisor
Kristina Lynch
Second Advisor
Robyn Millan
Third Advisor
Matthew Zettergren
Abstract
Measurements of Saturn’s radio and magnetic periodicities suggest that atmospheric forcing influences the magnetosphere-coupled current systems on the planet (Gurnett et al., 2007). A proposed mechanism for this phenomenon is that thermospheric heating drives strong neutral winds which drag ionospheric plasma and generate currents that close along magnetic field lines (Smith, 2011). However, the local current-closure physics of these processes is di!cult to isolate in global Saturn models even if they suggest neutral wind forcing is a plausible driver for these changes (Jia et al., 2012). This thesis uses the Earth-based auroral GEMINI (Geospace Environment Model of Ion-Neutral Interactions) model within a controlled proxy experiment to test how neutral winds modify current closure in a structured ionosphere (Zettergren & Semeter (2012) and Zettergren & Snively (2015)). Using an observed auroral event in March 2023, I compare varying neutral wind profiles and their effects on GEMINI outputs while holding the imposed electric potential and auroral precipitation structure fixed. I evaluate changes in perpendicular current divergence, field-aligned current (FAC) closure, and Joule heating to identify how the neutral wind dynamo functions within these simulations. The simulations suggest that stronger neutral wind forcing modifies FAC morphology and heating structure in ways that depend on wind direction. These results suggest that neutral winds can reorganize auroral current closure locally even when the system is not generating energy in net. This work aims to o"er insight into one-way coupling from neutrals to the magnetosphere and to inform future fully-coupled modeling e"orts both on Earth and at Saturn by clarifying how arc-scale wind forcing in structured ionospheres may influence these processes.
Recommended Citation
Gandhi, Shreya, "Pedersen by Proxy: Neutral Wind Drivers of the Magnetosphere" (2026). Physics and Astronomy Undergraduate Senior Theses. 3.
https://digitalcommons.dartmouth.edu/physics_senior_theses/3
