Does the Ionosphere and Plasmasphere Ever Vanish? : an Investigation of Topside Ionospheric Behavior During Geomagnetic Storms
Abstract
Utilizing data from two Swarm satellites and ground-based data from the Madrigal database, I set out to investigate the effects that geomagnetic storms have on the topside ionosphere and plasmasphere for medium and large geomagnetic storms. A previous study found that the ionosphere vTEC essentially dropped to zero at equatorial latitudes during the July 15/16, 2000 geomagnetic storm over South America. The purpose of this study is to examine how common severe ionosphere and plasmasphere depletions occur and offer insight into topside ionosphere and plasmasphere behavior during geomagnetic storm-times. Data were obtained for Swarm-A and Swarm-B from the onboard task management system (TMS). Slant and vertical TEC values were calculated during processing and obtained from the level-2 daily data files on the ESA website. Ground-based GPS TEC values were obtained from the Madrigal database. A single geomagnetically quiet day was used to allow for a geomagnetic storm- and quiet-time difference to observe the change in vTEC during storm conditions. The day before and after the storm were also compared to storm-time conditions. In situ density measurements onboard Swarm-A and Swarm-B were also utilized to compare storm- and quiet-time topside ionospheric densities and observe potential density gradients (the two satellites fly at different altitudes).We looked at data from the largest two geomagnetic storms from 2015-2019. For the storms studied, we did not find equatorial depletions in the aftermath of the storms other than the recurring daily depletions over the Pacific. These depletions were also present during quiet days and occurred in the afternoon and early evening. Our findings show that topside ionospheric and plasmaspheric vTEC tends to experience enhancement during all storm-time hours with a peak in vTEC centered around +/- five to ten degrees latitude (the vTEC enhancement appears stronger in the EIA peaks) and a local minimum near the equator (with enhancement still occurring at a lesser amount). In situ density measurements appear to model similar behavior as vTEC changes. During large storms, such as the 2015 St. Patrick's Day storm, a larger vTEC gradient is observed between Swarm-Alpha and Swarm-Bravo. The vTEC enhancement seen in the topside ionosphere at equatorial latitudes is likely due to the fountain effect and upwelling of the ionospheric column density during storm conditions. The larger gradients observed between Swarm-Alpha and Swarm-Bravo suggests that there could be a density drift eastward within the topside ionosphere and plasmasphere or that plasma bubbles form between 464 km and 521 km of altitude, but it is likely just the normal fall off from the F2 peak. Irregularities in the electron density appear in some early morning storm data and are possibly due to the formation of plasma bubbles. Currently, further work is being done to better understand the vTEC dependence based on storm intensity.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMED0040027R
- Keywords:
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- 0810 Post-secondary education;
- EDUCATION;
- 0855 Diversity;
- EDUCATION