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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 2
Ann. Geophys., 36, 509-525, 2018
https://doi.org/10.5194/angeo-36-509-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Ann. Geophys., 36, 509-525, 2018
https://doi.org/10.5194/angeo-36-509-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 29 Mar 2018

Regular paper | 29 Mar 2018

The effect of subauroral polarization streams on the mid-latitude thermospheric disturbance neutral winds: a universal time effect

Hui Wang1, Kedeng Zhang1,2, Zhichao Zheng1, and Aaron James Ridley3 Hui Wang et al.
  • 1Dept. of Space Physics, School of Electronic Information, Wuhan University, Hubei, 430072, China
  • 2National Center for Atmospheric Research, Boulder, CO 80301, USA
  • 3Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, USA

Abstract. The temporal and spatial variations in thermospheric neutral winds at an altitude of 400km in response to subauroral polarization streams (SAPS) are investigated using global ionosphere and thermosphere model simulations under the southward interplanetary magnetic field (IMF) condition. During SAPS periods the westward neutral winds in the subauroral latitudes are greatly strengthened at dusk. This is due to the ion drag effect, through which SAPS can accelerate neutral winds in the westward direction. The new findings are that for SAPS commencing at different universal times, the strongest westward neutral winds exhibit large variations in amplitudes. The ion drag and Joule heating effects are dependent on the solar illumination, which exhibit UT variations due to the displacement of the geomagnetic and geographic poles. With more sunlight, stronger westward neutral winds can be generated, and the center of these neutral winds shifts to a later magnetic local time than neutral winds with less solar illumination. In the Northern Hemisphere and Southern Hemisphere, the disturbance neutral wind reaches a maximum at 18:00 and 04:00UT, and a minimum at 04:00 and 16:00UT, respectively. There is a good correlation between the neutral wind velocity and cos0.5(SZA) (solar zenith angle). The reduction in the electron density and enhancement in the air mass density at an altitude of 400km are strongest when the maximum solar illumination collocates with the SAPS. The correlation between the neutral wind velocity and cos0.5(SZA) is also good during the northward IMF period. The effect of a sine-wave oscillation of SAPS on the neutral wind also exhibits UT variations in association with the solar illumination.

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For subauroral polarization streams (SAPS) commencing at different universal times (UT), the strongest westward neutral winds exhibit large variations in amplitudes. The effect of a sine-wave oscillation of SAPS on the neutral wind also exhibits UT variations in association with the solar illumination. The reduction in the electron density and enhancement in the air mass density are strongest when the maximum solar illumination collocates with the SAPS.
For subauroral polarization streams (SAPS) commencing at different universal times (UT), the...
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