Observations of dawn–dusk aligned polar cap aurora during the substorms of January 21, 2005 |
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Authors: | A.M. Du W. Sun B.T. Tsurutani R.N. Boroyev A.V. Moiseyev |
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Affiliation: | aInstitute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;bGeophysical Institute, University of Alaska Fairbanks, AK 99775, USA;cJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA;dYu.G. Shafer Institute of Cosmophysical Research and Aeronomy, Yakutsk, Russia |
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Abstract: | A new type of polar cap aurora, dawn–dusk aligned polar cap aurora (DDAPCA), was detected during the exceptionally intense January 21, 2005 substorm (AEmax=3504 nT). The DDAPCA was located at very high latitude (>85° MLAT) in the polar cap region. As the interplanetary magnetic field (IMF) GSM By component rotated from a positive to a negative value, the DDAPCA tilt angle relative to the dawn–dusk direction rotated anticlockwise and reached ∼45°. It is speculated that the DDAPCA arises from the formation of an X-line in the distant (>80RE) tail due to polar cap magnetic field reconnection under unusually high solar wind compression conditions. |
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Keywords: | Substorm Planetary shock Polar cap Aurora Reconnection |
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