University of Oulu

Oyama, Si., Aikio, A., Sakanoi, T. et al. Geomagnetic activity dependence and dawn-dusk asymmetry of thermospheric winds from 9-year measurements with a Fabry–Perot interferometer in Tromsø, Norway. Earth Planets Space 75, 70 (2023).

Geomagnetic activity dependence and dawn-dusk asymmetry of thermospheric winds from 9-year measurements with a Fabry–Perot interferometer in Tromsø, Norway

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Author: Oyama, Shin-ichiro1,2,3; Aikio, Anita3; Sakanoi, Takeshi4;
Organizations: 1Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan
2National Institute of Polar Research, Tachikawa, Japan
3Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
4Graduate School of Science Planetary Plasma and Atmospheric Research Center, Tohoku University, Sendai, Japan
5Department of Computer and Network Engineering, The University of Electro-Communications, Chofu, Japan
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.9 MB)
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Language: English
Published: Springer Nature, 2023
Publish Date: 2023-10-02


Ion drag associated with the ionospheric plasma convection plays an important role in the high-latitude thermospheric dynamics, yet changes in the thermospheric wind with geomagnetic activity are not fully understood. We performed a statistical analysis of the thermospheric wind measurements with a Fabry–Perot interferometer (FPI; 630 nm wavelength) in Tromsø, Norway, in the winter months for 9 years. The measurements were sorted by a SuperMAG (SME) index, and a quiet-time wind pattern was defined as an hourly mean under SME ≤ 40 nT. The quiet-time wind pattern can be expected to be represented by a pressure gradient associated with the solar radiation and a geostrophic force balance. With an increase in the geomagnetic activity level, the thermospheric wind turned over from eastward to westward at dusk and increased the equatorward magnitude from midnight to dawn. Deviations from the quiet-time wind presented similar patterns in the direction with the ionospheric plasma convection but were larger in magnitude at dusk than at dawn. This is the first study to report a dawn-dusk asymmetry of the thermospheric wind acceleration feature and signatures of the eastward wind acceleration at dawn by ion drag.

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Series: Earth, planets and space
ISSN: 1343-8832
ISSN-E: 1880-5981
ISSN-L: 1343-8832
Volume: 75
Issue: 1
Article number: 70
DOI: 10.1186/s40623-023-01829-0
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This work has been supported by JSPS KAKENHI JP 16H06286, 21H04518, 21K18651, 21KK0059, 22H01283, 22H00173 and 22K21345. H. V. was partially supported by AF314664.
Academy of Finland Grant Number: 314664
Detailed Information: 314664 (Academy of Finland Funding decision)
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