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| Titel |
On large plasmoid formation in a global magnetohydrodynamic simulation |
| VerfasserIn |
I. Honkonen, M. Palmroth, T. I. Pulkkinen, P. Janhunen  , A. Aikio |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 29, no. 1 ; Nr. 29, no. 1 (2011-01-14), S.167-179 |
| Datensatznummer |
250016956
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| Publikation (Nr.) |
 copernicus.org/angeo-29-167-2011.pdf |
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| Zusammenfassung |
| We investigate plasmoid formation in the magnetotail using the global
magnetohydrodynamic (MHD) simulation GUMICS-4. Here a plasmoid implies a
major reconfiguration of the magnetotail where a part of the tail plasma
sheet is ejected downstream, in contrast to small Earthward-propagating
plasmoids. We define a plasmoid based solely on the structure of the closed
(connected to the Earth at both ends) magnetic field line region. In this
definition a plasmoid is partly separated from the ordinary closed field line
region by lobe field lines or interplanetary field lines resulting from lobe
reconnection. We simulate an event that occurred on 18 February 2004 during which
four intensifications of the auroral electroject (AE) index occurred in 8 h.
Plasmoids form in the simulation for two of the four AE
intensifications. Each plasmoid forms as a result of two consecutive large
and fast rotations of the interplanetary magnetic field (IMF). In both cases
the IMF rotates 180 degrees at 10 degrees per minute, first from southward to
northward and some 15 min later from northward to southward. The other
two AE intencifications however are not associated with a plasmoid formation.
A plasmoid does not form if either the IMF rotation speed or the angular
change of the rotation are small. We also present an operational definition
for these fully connected plasmoids that enables their automatic detection in
simulations. Finally, we show mappings of the plasmoid footpoints in the
ionosphere, where they perturb the polar cap boundary in both hemispheres. |
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