Medium Scale Travelling Ionospheric Disturbances (MSTIDs) are quasi-wavelike structures in ionospheric density that can be sensed using Global Navigational Satellite Service (GNSS) Total Electron Content (TEC) techniques and coherent scatter radars such as the Super Dual Auroral Radar Network (SuperDARN). MSTIDs, especially those observed during quiet times and on the night side, have been known to be driven by electrodynamic instability processes, such as the Perkins instability. In this work, SuperDARN is used in conjunction with GNSS TEC data to investigate MSTIDs during a major geomagnetic storm on September 7-8th, 2017. The interval of this study is in the North American region between 23UT and 3UT, during the peak of the storm, when Kp reached 9. MSTIDs during the interval were investigated by previous studies. However, the roles of electrodynamic instability processes and atmospheric gravity waves (AGWs) in driving the MSTIDs were not determined. GNSS TEC fluctuations associated with the MSTIDs were strong, reaching up to half of background TEC. In SuperDARN, MSTID signatures were observed in power measurements. Meanwhile, SuperDARN line-of-sight (LOS) plasma velocity corresponding to MSTID structures exceeded $pm$500 m/s. This systemic change in the polarity of SuperDARN LOS velocities is indicative of strong polarization electric fields and therefore driving electrodynamic instability processes. This work therefore presents signatures of storm time electrified MSTIDs in mid-latitude North America. / Master of Science / The upper atmosphere contains a region called the ionosphere, where ionized gas called plasma exists. This plasma can be sensed using satellites and ground-based receivers. Specifically, Global Navigational Satellite Service constellations, such as GPS, are good candidates for this technique. This method yields a column density measurement of electrons and is known as GNSS TEC. Most of the time, GNSS TEC is used in a low resolution format, but a high-resolution format is available. This high-resolution GNSS TEC allows for smaller structures in the ionosphere to be investigated. Ionospheric plasma can also be sensed using ground based radar systems, such as the Super Dual Auroral Radar Network (SuperDARN). Combining GNSS TEC and SuperDARN allows for investigation of disturbed structures in the Ionosphere. These structures include wave-like behavior, with time scales under 30 minutes, called Medium Scale Travelling Ionospheric Disturbances (MSTIDs). When these MSTIDs are investigated during times where the Sun is especially active, some unexpected results are found. Most importantly, SuperDARN radars see plasma velocity behave as if it is affected by MSTID structures. This suggests that the buoyancy force which drives the MSTIDs is an electric force instead of a pressure gradient. This behavior has been shown before, but only at night times, specifically when the Sun is not as active. Therefore, this work presents a new kind of MSTIDs.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/111790 |
| Date | 09 September 2022 |
| Creators | Kelley, Ian James |
| Contributors | Electrical Engineering, Baker, Joseph Benjamin, Ruohoniemi, John Michael, Bailey, Scott M., Scales, Wayne A. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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