1. Unexpected STEVE Observations at High Latitude During Quiet Geomagnetic Conditions.
- Author
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Gallardo‐Lacourt, B., Nishimura, Y., Kepko, L., Spanswick, E. L., Gillies, D. M., Knudsen, D. J., Burchill, J. K., Skone, S. H., Pinto, V. A., Chaddock, D., Kuzub, J., and Donovan, E. F.
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ATMOSPHERE , *SPACE environment , *MAGNETIC storms , *AURORAS , *ION migration & velocity , *SOLAR wind - Abstract
Strong Thermal Emission Velocity Enhancement (STEVE), is a captivating optical phenomenon typically observed in the mid‐latitude ionosphere. This paper presents an intriguing observation of a STEVE event at high‐latitudes, approximately 10 degrees poleward of previously documented observations. This event was recorded in Yellowknife, Canada, by a TREx RGB imager and a citizen scientist. Swarm satellites traversed the latitude of the observation, measuring extreme westwards ion drift velocities exceeding 4 km/s. Such velocities are more typically associated with the subauroral region located at mid‐latitudes, rather than at the high‐latitudes reported here. Significantly, this event occurred without a substorm, which differs from previous STEVE observations. While high‐latitude radars detected fast ionospheric equatorward flows, GOES satellite did not record any injections. These observations suggest that the inner magnetosphere is highly inflated. This unique case study raises new questions surrounding subauroral dynamics and the influence of magnetospheric configurations on ionospheric responses. Plain Language Summary: Strong Thermal Emission Velocity Enhancement, also known as STEVE, is a fascinating nighttime optical phenomenon that takes place in the upper part of Earth's atmosphere. It can be easily recognized by its distinctive appearance as a narrow white‐mauve arc that is associated with strong westward flows and is situated just equatorward of the auroral oval. Previous research has shown that STEVE events occur together with intense ionospheric flows and occur after specific disturbances in the near‐Earth space environment known as substorms. They have found that substorms are important for creating the special conditions that lead to STEVE and other subauroral enhancements. In our study, we focus on a unique STEVE event that did not occur after a substorm. Furthermore, this observation took place under remarkably quiet solar wind conditions; nevertheless, strong ionospheric flows were recorded. This unusual case raises new questions about the atmospheric responses and how it is affected by the configuration of the magnetic field in space. By investigating these special circumstances, we hope to learn more about STEVE and its causes, which will help us advance our knowledge in the complex ionosphere‐magnetosphere‐solar wind coupled system. Key Points: Non‐storm and non‐substorm Strong Thermal Emission Velocity Enhancement (STEVE) occurrenceStrong subauroral flows during quiet geomagnetic conditionsThe ionospheric electrodynamics of this STEVE event differ from previous studies [ABSTRACT FROM AUTHOR]
- Published
- 2024
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