Date of Award
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Space Science
Committee Chair
Gary Zank
Committee Member
Gang Lu
Committee Member
Qiang Hu
Committee Member
Lingling Zhao
Research Advisor
Ying Zou
Subject(s)
Winds aloft, Ionosphere, Magnetosphere
Abstract
High-latitude neutral winds have a number of drivers, both from solar and magnetospheric origins as well as from the lower atmosphere. The efficiency of the individual thermospheric forces, in addition to the relative strength of ion-neutral coupling, are not well characterized. Because of this, the neutral wind response to changes in ionospheric convection is not well understood, with response times ranging on the order of tens of minutes to hours. Using both data driven and modeling simulation efforts, we aim to develop a better understanding of high-latitude ionosphere-thermosphere coupling. In order to do this, three individual studies will be done to answer the following questions: 1) What is the time-scale of neutral wind's response to changes in magnetospheric and auroral forcing? 2) How does this ion-neutral coupling efficiency change with varying levels of geomagnetic activity? 3) What is the relative contribution of each of the thermospheric forces, and what forces dominate neutral wind responses? Using data from Scanning Doppler Imagers (SDIs), the Poker Flat Incoherent Scatter Radar (PFISR), and All Sky Imagers (ASIs), a new neutral wind response time calculation method is developed. This method differs from previous calculation methods, such as the e-folding time and time-lagged correlation analysis, by providing a time evolution of the response time that considers all thermospheric forces. Using this new response time calculation, we perform a statistical analysis of neutral wind responses to magnetospheric forcing. Then, we investigate how this response time changes with respect to geomagnetic activity level by performing a superposed epoch analysis on the short and long response events to uncover what geomagnetic conditions lead to faster or longer response times. This analysis will be done using the AE index, SYM/H index, OMNI IMF data, local magnetometer data from the THEMIS ground array and electron density from PFISR. For our modeling efforts, the thermosphere-ionosphere-electrodynamics global circulation model (TIE-GCM) is used to investigate the influence of various high-latitude ionospheric drivers of thermospheric winds during a storm period. Individual thermospheric forcing terms are also calculated in order to identify dominant drivers of the neutral winds.
Recommended Citation
Davidson, Katherine, "F-region neutral wind responses to magnetospheric forcing in the nightside auroral oval" (2025). Dissertations. 448.
https://louis.uah.edu/uah-dissertations/448
