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Storm Time Electrified MSTIDs Observed over Mid-Latitude North America
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  • Ian James Kelley,
  • Bharat Simha Reddy Kunduri,
  • J. B. H. Baker,
  • John Michael Ruohoniemi,
  • Simon George Shepherd
Ian James Kelley
Virginia Tech

Corresponding Author:ikelley@vt.edu

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Bharat Simha Reddy Kunduri
Virginia Tech
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J. B. H. Baker
Virginia Tech
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John Michael Ruohoniemi
Virginia Tech
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Simon George Shepherd
Dartmouth College
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Abstract

Medium-scale Traveling Ionospheric Disturbances (MSTIDs) are prominent and ubiquitous features of the mid-latitude ionosphere, and are observed in Super Dual Auroral Radar Network (SuperDARN) and high-resolution Global Navigational Satellite Service (GNSS) Total Electron Content (TEC) data. The mechanisms driving these MSTIDs are an open area of research, especially during geomagnetic storms. Previous studies have demonstrated that night-side MSTIDs are associated with an electrodynamic instability mechanism like Perkins, especially during geomagnetically quiet conditions. However, day-side MSTIDs are often associated with atmospheric gravity waves. Very few studies have analyzed the mechanisms driving MSTIDs during strong geomagnetic storms at mid-latitudes. In this study, we present mid-latitude MSTIDs observed in de-trended GNSS TEC data and SuperDARN radars over the North American sector, during a geomagnetic storm (peak Kp reaching 9) on September 7-8, 2017. In SuperDARN, MSTIDs were observed in ionospheric backscatter with Line Of Sight (LOS) velocities exceeding 800 m/s. Additionally, radar LOS velocities oscillated with amplitudes reaching +/-$500 m/s as the MSTIDs passed through the fields-of-view. In detrended TEC, these MSTIDs produced perturbations reaching ~50 percent of background TEC magnitude. The MSTIDs were observed to propagate in the westward/south-westward direction with a time period of ~15 minutes. Projecting de-trended GNSS TEC data along SuperDARN beams showed that enhancements in TEC were correlated with enhancements in SuperDARN SNR and positive LOS velocities. Finally, SuperDARN LOS velocities systematically switched polarities between the crests and the troughs of the MSTIDs, indicating the presence of polarization electric fields and an electrodynamic instability process during these MSTIDs.