University of Oulu

Oyama, Si., Vanhamäki, H., Cai, L. et al. Thermospheric wind response to a sudden ionospheric variation in the trough: event at a pseudo-breakup during geomagnetically quiet conditions. Earth Planets Space 74, 154 (2022).

Thermospheric wind response to a sudden ionospheric variation in the trough : event at a pseudo-breakup during geomagnetically quiet conditions

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Author: Oyama, Shin-ichiro1,2,3; Vanhamäki, Heikki3; Cai, Lei3;
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
4European Incoherent Scatter Association, Tromsø, Norway
5Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
6Finnish Meteorological Institute, Helsinki, Finland
7Polar Geophysical Institute, Apatity, Russia
8Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan
9Department of Computer and Network Engineering, The University of Electro-Communications, Chofu, Japan
10Graduate School of Science Planetary Plasma and Atmospheric Research Center, Tohoku University, Sendai, Japan
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.2 MB)
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Language: English
Published: Springer Nature, 2022
Publish Date: 2023-06-12


The thermospheric wind response to a sudden westward turning of the ion velocity at a high latitude was studied by analyzing data obtained with a Fabry–Perot interferometer (FPI; 630 nm), Dynasonde, and Swarm A & C satellites during a conjunction event. The event occurred during a geomagnetically quiet period (Kp = 0 +) through the night, but some auroral activity occurred in the north. The collocated FPI and Dynasonde measured the thermospheric wind (U) and ionospheric plasma velocity (V), respectively, in the F region at the equatorward trough edge. A notable scientific message from this study is the possible role of thermospheric wind in the energy dissipation process at F-region altitude. The FPI thermospheric wind did not instantly follow a sudden V change due to thermospheric inertia in the F region. At a pseudo-breakup during the event, V suddenly changed direction from eastward to westward within 10 min. U was concurrently accelerated westward, but its development was more gradual than that of V, with U remaining eastward for a while after the pseudo-breakup. The delay of U is attributed to the thermospheric inertia. During this transition interval, U∙V was negative, which would result in more efficient generation of frictional heating than the positive U∙V case. The sign of U∙V, which is related to the relative directions of the neutral wind and plasma drift, is important because of its direct impact on ion-neutral energy exchange during collisions. This becomes especially important during substorm events, where rapid plasma velocity changes are common. The sign of U∙V may be used as an indicator to find the times and locations where thermospheric inertia plays a role in the energy dissipation process.

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Series: Earth, planets and space
ISSN: 1343-8832
ISSN-E: 1880-5981
ISSN-L: 1343-8832
Volume: 74
Issue: 1
Article number: 154
DOI: 10.1186/s40623-022-01710-6
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, and JPJSBP120194814. H. V. was partially supported by AF314664. This work was carried out by the joint research program of Planetary Plasma and Atmospheric Research Center, Tohoku University.
Academy of Finland Grant Number: 314664
Detailed Information: 314664 (Academy of Finland Funding decision)
Dataset Reference: All-sky camera images at Abisko, Kilpisjärvi, Longyearbyen, and Lovozero and the EISCAT Dynasonde data were obtained from individual PIs (Sodankylä Geophysical Observatory, Finland; Finnish Meteorological Institute, Finland; National Institute of Polar Research, Japan; and Polar Geophysical Institute, Russia; EISCAT Tromsø, Norway) after checking the quick-looks at their websites (,,, The Swarm data were obtained through their websites ( The FPI quick-looks are available at Access and processing data of the solar wind and geomagnetic indices were obtained using SPEDAS V4.1 through Package of the CHAOS-7 model code was downloaded from
Copyright information: © The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit