ORCID Identifier(s)

0000-0002-0076-7338

Graduation Semester and Year

2023

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics and Applied Physics

Department

Physics

First Advisor

Ramon E Lopez

Second Advisor

Alex Weiss

Abstract

The interaction between the dynamically changing solar wind and Earth’s magnetosphere results in several different current systems. The most relevant to space weather are the Birkeland currents, a.k.a field-aligned currents (FACs), that couple the magnetosphere to the ionosphere. These currents flow into and out of the ionosphere and are closed through the ionosphere by the horizontally flowing eastward and westward electrojets. This FAC-electrojet current system is responsible for some of the most beautiful and detrimental space weather impacts. The aurora borealis (or northern lights) in the Northern Hemisphere and aurora australis (or southern lights) in the Southern Hemisphere are displays of lights resulting from energetic particles that have travels from the sun, through interplanetary space, down Earth’s magnetic field lines and into Earth’s polar region. These downward flowing particles are responsible for upward flowing FACs. On the contrary, the FAC-electrojet current system can cause major disturbances. These ionospheric currents have been known to destroy satellites, erode pipelines, and disrupt the power grid. The Space Weather Prediction Center (SWPC) use global magnetohydrodynamic (MHD) models to nowcast and forecast space weather in an attempt to forewarn society about potential space weather impacts. So, it is imperative that we investigate the dynamics and processes that affect the magnitude of these ionospheric currents. To do this, we take a two way approach in which we first look to investigate how these currents behave in reality. Then we look to determine how well do global MHD models reproduce the observed behaviors and magnitudes of these currents. Specifically, we investigate the role seasonal inter- hemispheric asymmetry in conductance play in controlling the amount of ionospheric current using observations and simulating complementary models. From observations we find that in the summer the currents increase in magnitude with increasing solar wind electric field and F10.7. In the winter, the currents decrease with increasing F10.7, as a consequence of a decreased geoeffective length. We also validate current-closure as seen by the observed FAC-electrojet relationship. This linear relationship is also reproduced by SWMF, despite the model’s underestimation of the magnitudes of the currents and inability to replicate reality at times. The model does not always reproduce the behavior of the currents with increasing F10.7, but it does reproduce the expected behavior in the potential. This points to the need for improved conductivity models within global MHD models.

Keywords

space physics, ionosphere, currents, asymmetry, F10.7, FAC

Disciplines

Physical Sciences and Mathematics | Physics

Comments

Degree granted by The University of Texas at Arlington

Included in

Physics Commons

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