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  The asymmetric geospace as displayed during the geomagnetic storm on 17. August 2001

Østgaard, N., Reistad, J. P., Tenfjord, P., Laundal, K. M., Rexer, T., Haaland, S., et al. (2018). The asymmetric geospace as displayed during the geomagnetic storm on 17. August 2001. Annales Geophysicae, 36, 1577-1596. doi:10.5194/angeo-36-1577-2018.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0003-9F24-2 Version Permalink: http://hdl.handle.net/21.11116/0000-0003-9F25-1
Genre: Journal Article

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 Creators:
Østgaard, Nikolai, Author
Reistad, Jone P., Author
Tenfjord, Paul, Author
Laundal, Karl M., Author
Rexer, Theresa, Author
Haaland, Stein1, Author              
Snekvik, Kristian, Author
Hesse, Michael, Author
Milan, Stephen E., Author
Ohma, Anders, Author
Affiliations:
1Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832288              

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 Abstract: Previous studies have shown that conjugate auroral features are displaced in the two hemispheres when the interplanetary magnetic field (IMF) has a transverse (Y) component. It has also been shown that a BY component is induced in the closed magnetosphere due to the asymmetric loading of magnetic flux in the lobes following asymmetric dayside reconnection when the IMF has a Y component. The magnetic field lines with azimuthally displaced footpoints map into a “banana”-shaped convection cell in one hemisphere and an “orange”-shaped cell in the other. Due to the Parker spiral our system is most often exposed to a BY-dominated IMF. The dipole tilt angle, varying between ±34∘, leads to warping of the plasma sheet and oppositely directed BY components in dawn and dusk in the closed magnetosphere. As a result of the Parker spiral and dipole tilt, geospace is asymmetric most of the time. The magnetic storm on 17 August 2001 offers a unique opportunity to study the dynamics of the asymmetric geospace. IMF BY was 20–30 nT and tilt angle was 23∘. Auroral imaging revealed conjugate features displaced by 3–4 h magnetic local time. The latitudinal width of the dawnside aurora was quite different (up to 6∘) in the two hemispheres. The auroral observations together with convection patterns derived entirely from measurements indicate dayside, lobe and tail reconnection in the north, but most likely only dayside and tail reconnection in the Southern Hemisphere. Increased tail reconnection during the substorm expansion phase reduces the asymmetry.

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Language(s): eng - English
 Dates: 2018
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.5194/angeo-36-1577-2018
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Title: Annales Geophysicae
Source Genre: Journal
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Publ. Info: Montrouge Cedex, France : Gauthier-Villars
Pages: - Volume / Issue: 36 Sequence Number: - Start / End Page: 1577 - 1596 Identifier: ISSN: 0992-7689
CoNE: https://pure.mpg.de/cone/journals/resource/954928606127