University of Oulu

Zhou, S., Luan, X., Søraas, F., Østgaard, N., & Raita, T. ( 2018). The detached auroras induced by the solar wind pressure enhancement in both hemispheres from imaging and in situ particle observations. Journal of Geophysical Research: Space Physics, 123, 3170– 3182.

The detached auroras induced by the solar wind pressure enhancement in both hemispheres from imaging and in situ particle observations

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Author: Zhou, Su1,2; Luan, Xiaoli1; Søraas, Finn2;
Organizations: 1CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China
2Birkeland Centre for Space Science, University of Bergen, Bergen, Norway
3Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.9 MB)
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Language: English
Published: American Geophysical Union, 2018
Publish Date: 2019-09-23


This paper presents simultaneous detached proton auroras that appeared in both hemispheres at 11:06 UT, 08 March 2012, just 2 min after a sudden solar wind pressure enhancement (~11:04 UT) hit the Earth. They were observed under northward interplanetary magnetic field Bz condition and during the recovery phase of a moderate geomagnetic storm. In the Northern Hemisphere, Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observed that the detached arc occurred within 60°–65° magnetic latitude and covered a few magnetic local time (MLT) hours ranging from 0530 to 0830 MLT with a possible extension toward noon. At the same time (11:06 UT), Polar Orbiting Environment Satellites 19 detected a detached proton aurora around 1300 MLT in the Southern Hemisphere, centering ~62° magnetic latitude, which was at the same latitudes as the northern detached arc. This southern aurora was most probably a part of a dayside detached arc that was conjugate to the northern one. In situ particle observations indicated that the detached auroras were dominated by protons/ions with energies ranging from around 20 keV to several hundreds of keV, without obvious electron precipitations. These detached arcs persisted for less than 6 min, consistent with the impact from pressure enhancement and the observed electromagnetic ion cyclotron (EMIC) waves. It is suggested that the increasing solar wind pressure pushed the hot ions in the ring current closer to Earth where the steep gradient of cold plasma favored EMIC wave growth. By losing energy to EMIC waves the energetic protons (>20 keV) were scattered into the loss cone and produced the observed detached proton auroras.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 123
Issue: 4
Pages: 3170 - 3182
DOI: 10.1002/2017JA024562
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This study was supported by the Research Council of Norway under contract 223252/F50 (CoE), National Natural Science Foundation of China (41674154, 41421063, and 41325017), the Project of Chinese Academy of Sciences (KZZD‐EW‐01) of the Chinese Academy of Sciences, and the Fundamental Research Funds for the Central Universities (WK2080000077).
Copyright information: © 2018. American Geophysical Union. All Rights Reserved.