Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study
We investigate with the help of a magnetohydrodynamic (MHD) model how the large-scale topology of the magnetosphere develops for a constant interplanetary magnetic field (IMF) with different IMF clock angles and for an IMF <i>B<sub>y</sub></i> sign change during northward...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2004-03-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/22/951/2004/angeo-22-951-2004.pdf |
| _version_ | 1828768038298583040 |
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| author | A. Kullen P. Janhunen |
| author_facet | A. Kullen P. Janhunen |
| author_sort | A. Kullen |
| collection | DOAJ |
| description | We investigate with the help of a magnetohydrodynamic (MHD) model how the
large-scale
topology of the magnetosphere develops for a constant interplanetary
magnetic field (IMF) with different
IMF clock angles and for an IMF <i>B<sub>y</sub></i> sign change during northward IMF.
A detailed examination of the topological changes in the tail and the
ionosphere for different IMF conditions shows a good agreement with
observational results.
</p><p style="line-height: 20px;">
The MHD simulations for different constant IMF clock angle cases
show the expected field-line bending and tail twisting for nonzero
IMF <i>B<sub>y</sub></i>.
The tail becomes longer and at its tailward end stronger twisted for
IMF <i>B<sub>z</sub></i>>∣<i>B<sub>y</sub></i>∣ than for IMF <i>B<sub>z</sub></i><∣<i>B<sub>y</sub></i>∣. The field
lines originating in the high-latitude flank of the far-tail plasma
sheet map into the near-Earth tail lobes and to a strongly poleward
displaced polar cap boundary. A comparison with observations suggests
that an oval-aligned arc may occur on the high-latitude part of the
polar cap boundary.
</p><p style="line-height: 20px;">
An IMF <i>B<sub>y</sub></i> sign change causes large deformations of the tail.
After the IMF <i>B<sub>y</sub></i> flip the near-Earth and far-tail plasma sheet
regions are oppositely twisted which causes in the near-Earth tail a
bifurcation of the closed field line region that moves from one flank to
the other.
The bifurcated part of the closed field line region maps to a bridge
of closed field lines moving over the entire polar cap. This moving
bridge may be interpreted as the mapped region of a moving
transpolar arc. Based on earlier observations, such a type of polar
arcs is expected to occur after an IMF <i>B<sub>y</sub></i> sign change.<br><br>
<b>Key words. </b>Ionosphere (auroral ionosphere; ionospheremagnetosphere
interactions). Space plasma physics (numerical
simulation studies) |
| first_indexed | 2024-12-11T07:39:26Z |
| format | Article |
| id | doaj.art-9156f4c89b1147d2aa5fb972dfb744ba |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-11T07:39:26Z |
| publishDate | 2004-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-9156f4c89b1147d2aa5fb972dfb744ba2022-12-22T01:15:37ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762004-03-012295197010.5194/angeo-22-951-2004Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation studyA. Kullen0P. Janhunen1Alfvén Laboratory, Royal Institute of Technology, Stockholm, SwedenGeophysical Research, Finnish Meteorological Institute, Helsinki, FinlandWe investigate with the help of a magnetohydrodynamic (MHD) model how the large-scale topology of the magnetosphere develops for a constant interplanetary magnetic field (IMF) with different IMF clock angles and for an IMF <i>B<sub>y</sub></i> sign change during northward IMF. A detailed examination of the topological changes in the tail and the ionosphere for different IMF conditions shows a good agreement with observational results. </p><p style="line-height: 20px;"> The MHD simulations for different constant IMF clock angle cases show the expected field-line bending and tail twisting for nonzero IMF <i>B<sub>y</sub></i>. The tail becomes longer and at its tailward end stronger twisted for IMF <i>B<sub>z</sub></i>>∣<i>B<sub>y</sub></i>∣ than for IMF <i>B<sub>z</sub></i><∣<i>B<sub>y</sub></i>∣. The field lines originating in the high-latitude flank of the far-tail plasma sheet map into the near-Earth tail lobes and to a strongly poleward displaced polar cap boundary. A comparison with observations suggests that an oval-aligned arc may occur on the high-latitude part of the polar cap boundary. </p><p style="line-height: 20px;"> An IMF <i>B<sub>y</sub></i> sign change causes large deformations of the tail. After the IMF <i>B<sub>y</sub></i> flip the near-Earth and far-tail plasma sheet regions are oppositely twisted which causes in the near-Earth tail a bifurcation of the closed field line region that moves from one flank to the other. The bifurcated part of the closed field line region maps to a bridge of closed field lines moving over the entire polar cap. This moving bridge may be interpreted as the mapped region of a moving transpolar arc. Based on earlier observations, such a type of polar arcs is expected to occur after an IMF <i>B<sub>y</sub></i> sign change.<br><br> <b>Key words. </b>Ionosphere (auroral ionosphere; ionospheremagnetosphere interactions). Space plasma physics (numerical simulation studies)https://www.ann-geophys.net/22/951/2004/angeo-22-951-2004.pdf |
| spellingShingle | A. Kullen P. Janhunen Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study Annales Geophysicae |
| title | Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study |
| title_full | Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study |
| title_fullStr | Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study |
| title_full_unstemmed | Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study |
| title_short | Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study |
| title_sort | relation of polar auroral arcs to magnetotail twisting and imf rotation a systematic mhd simulation study |
| url | https://www.ann-geophys.net/22/951/2004/angeo-22-951-2004.pdf |
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