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| Titel |
Dynamical response of the magnetotail to changes of the solar wind direction: an MHD modeling perspective |
| VerfasserIn |
V. A. Sergeev, N. A. Tsyganenko, V. Angelopoulos |
| 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 ; 26, no. 8 ; Nr. 26, no. 8 (2008-08-06), S.2395-2402 |
| Datensatznummer |
250016197
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| Publikation (Nr.) |
 copernicus.org/angeo-26-2395-2008.pdf |
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| Zusammenfassung |
| We performed global MHD simulations to investigate the magnetotail
response to the solar wind directional changes (Vz-variations).
These changes, although small, cause significant variations of the
neutral sheet shape and location even in the near and middle tail
regions. They display a complicated temporal response, in which
~60 to 80% of the final shift of the neutral sheet in Z
direction occurs within first 10–15 min (less for faster
solar wind), whereas a much longer time (exceeding half hour) is
required to reach a new equilibrium. The asymptotic equilibrium
shape of the simulated neutral sheet is consistent with
predictions of Tsyganenko-Fairfield (2004) empirical model. To
visualize a physical origin of the north-south tail motion we
compared the values of the total pressure in the northern and
southern tail lobes and found a considerable difference (10–15%
for only 6° change of the solar wind direction used in the
simulation). That difference builds up during the passage of the
solar wind directional discontinuity and is responsible for the
vertical shift of the neutral sheet, although some pressure
difference remains in the near tail even near the new equilibrium.
Surprisingly, at a given tailward distance, the response was found
to be first initiated in the tail center (the "leader effect"),
rather than near the flanks, which can be explained by the wave
propagation in the tail, and which may have interesting
implications for the substorm triggering studies. The present
results have serious implications for the data-based modeling, as
they place constraints on the accuracy of tail magnetic
configurations to be derived for specific events using data of
multi-spacecraft missions, e.g. such as THEMIS. |
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