The asymmetric geospace as displayed during the geomagnetic storm on 17 August 2001
| Autor: | Nikolai Østgaard, Anders Ohma, Paul Tenfjord, Michael Hesse, Stephen E. Milan, Karl Magnus Laundal, Stein Haaland, Kristian Snekvik, Theresa Rexer, Jone Peter Reistad |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Atmospheric Science
010504 meteorology & atmospheric sciences Magnetosphere Astrophysics 01 natural sciences VDP::Mathematics and natural science: 400::Physics: 430 0103 physical sciences Substorm Earth and Planetary Sciences (miscellaneous) Astrophysics::Solar and Stellar Astrophysics Interplanetary magnetic field lcsh:Science 010303 astronomy & astrophysics 0105 earth and related environmental sciences Convection cell Geomagnetic storm Physics VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430 lcsh:QC801-809 Plasma sheet Geology Astronomy and Astrophysics lcsh:QC1-999 lcsh:Geophysics. Cosmic physics Space and Planetary Science Local time Physics::Space Physics lcsh:Q Heliospheric current sheet lcsh:Physics |
| Zdroj: | Annales Geophysicae, Vol 36, Pp 1577-1596 (2018) Annales Geophysicae |
| ISSN: | 1432-0576 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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