Effects of Subauroral Polarization Streams on the Upper Thermospheric Winds During Non‐Storm Time. Issue 5 (27th April 2022)

• Record Type: Journal Article
• Authors: Zou, Ying; Lyons, Larry R.; Shi, Xueling; Liu, Jiang; Wu, Qian; Conde, Mark; Shepherd, Simon G.; Mende, Stephen; Zhang, Yongliang; Coster, Antea
• Is Part Of: Journal of geophysical research. Volume 127:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-27
• Subjects: SAPS -- upper thermosphere -- neutral wind -- ion‐neutral coupling; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA029988
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Intense sunward (westward) plasma flows, named Subauroral Polarization Stream (SAPS), have been known to occur equatorward of the electron auroras for decades, yet their effect on the upper thermosphere has not been well understood. On the one hand, the large velocity of SAPS results in large momentum exchange upon each ion‐neutral collision. On the other hand, the low plasma density associated with SAPS implies a low ion‐neutral collision frequency. We investigate the SAPS effect during non‐storm time by utilizing a Scanning Doppler Imager (SDI) for monitoring the upper thermosphere, SuperDARN radars for SAPS, all‐sky imagers and DMSP Spectrographic Imager for the auroral oval, and GPS receivers for the total electron content. Our observations suggest that SAPS at times drives substantial (>50 m/s) westward winds at subauroral latitudes in the dusk‐midnight sector, but not always. The occurrence of the westward winds varies with AE index, plasma content in the trough, and local time. The latitudinally averaged wind speed varies from 60 to 160 m/s, and is statistically 21% of the plasma. These westward winds also shift to lower latitude with increasing AE and increasing MLT. We do not observe SAPS driving poleward wind surges, neutral temperature enhancements, or acoustic‐gravity waves, likely due to the somewhat weak forcing of SAPS during the non‐storm time. Key Points: Subauroral Polarization Stream (SAPS) at times drives substantial (>; 50‐m/s) westward winds at subauroral latitudes in the dusk‐midnight sector, but not always The occurrence of the SAPS‐driven winds varies with AE index, plasma content in the trough, and the local time The wind speed is 21% of SAPS flow, implying a weaker ion‐neutral coupling during non‐storm than active time