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Abstract Using Defense Meteorological Satellite Program (DMSP) and National Oceanic and Atmospheric Administration (NOAA) satellite observations and ground‐based observations by the THEMIS all‐sky imagers (ASIs) and SuperDARN radars, we determine how the equatorward boundary locations of ring current ions and plasma sheet electrons at pre‐midnight relate to occurrence of strong thermal emission velocity enhancement (STEVE) and intense subauroral ion drifts (SAID) during substorms. We found that the STEVE events are associated with a sharper gradient of electron precipitating flux, lower precipitating ion flux, and a narrower (<1°) latitudinal gap between the equatorward boundaries of trapped ring current ions and precipitating plasma sheet electrons and narrower region‐2 field‐aligned currents (FACs) than for the non‐STEVE events. The narrow gap of the particle boundaries contains intense SAID, higher upflow velocity, lower trough density, and slightly higher electron temperature than those for the non‐STEVE events. The non‐STEVE substorms have much wider gaps between the trapped ions and precipitating electrons, and subauroral polarization streams (SAPS) do not show intense SAID. These results indicate that subauroral flows and downward FACs for the STEVE events can only flow within the latitudinally narrow subauroral low‐conductance region between the ion and electron boundaries, resulting in intense SAID and heating. During the non‐STEVE events, the SAPS flows can flow in the latitudinally wide region without forming intense SAID.
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Exploring the relationship between STEVE and SAID during three events observed by SuperDARN
The phenomenon known as strong thermal emission velocity enhancement (STEVE) is a narrow optical structure that may extend longitudinally for thousands of kilometers. Initially observed by amateur photographers, it has recently garnered researchers’ attention. STEVE has been associated with a rapid westward flow of ions in the ionosphere, known as subauroral ion drift (SAID). In this work, we investigate three occurrences of STEVE, using data from one of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) ground-based all-sky imagers (ASIs) located at Pinawa, Manitoba, and from the Super Dual Auroral Radar Network (SuperDARN). This approach allows us to verify the correlation between STEVE and SAID, as well as analyze the temporal variation of SAID observed during STEVE events. Our results suggest that the SAID activity starts before the STEVE, and the magnitude of the westward flow decreases as the STEVE progresses toward the end of its optical manifestation.
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- PAR ID:
- 10559762
- Publisher / Repository:
- frontiers
- Date Published:
- Journal Name:
- Frontiers in Astronomy and Space Sciences
- Volume:
- 11
- ISSN:
- 2296-987X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fspas.2024.1422164
