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| Titel |
Effects of a solar wind dynamic pressure increase in the magnetosphere and in the ionosphere |
| VerfasserIn |
L. Juusola, K. Andréeová, O. Amm, K. Kauristie, S. E. Milan, M. Palmroth, N. Partamies |
| 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 ; 28, no. 10 ; Nr. 28, no. 10 (2010-10-27), S.1945-1959 |
| Datensatznummer |
250016902
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1945-2010.pdf |
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| Zusammenfassung |
| On 17 July 2005, an earthward bound north-south oriented magnetic cloud and
its sheath were observed by the ACE, SoHO, and Wind solar wind monitors. A
steplike increase of the solar wind dynamic pressure during northward
interplanetary magnetic field conditions was related to the leading edge of
the sheath. A timing analysis between the three spacecraft revealed that this
front was not aligned with the GSE y-axis, but had a normal
(−0.58,0.82,0). Hence, the first contact with the magnetosphere occurred on
the dawnside rather than at the subsolar point. Fortunately, Cluster, Double
Star 1, and Geotail happened to be distributed close to the magnetopause in
this region, which made it possible to closely monitor the motion of the
magnetopause. After the pressure front had impacted the magnetosphere, the
magnetopause was perceived first to move inward and then immediately to
correct the overshoot by slightly expanding again such that it ended up
between the Cluster constellation with Double Star 1 inside the magnetosphere
and Geotail in the magnetosheath. Coinciding with the inward and subsequent
outward motion, the ground-based magnetic field at low latitudes was observed
to first strengthen and then weaken. As the magnetopause position stabilised,
so did the ground-based magnetic field intensity, settling at a level
slightly higher than before the pressure increase. Altogether the
magnetopause was moving for about 15 min after its first contact with the
front. The high latitude ionospheric signature consisted of two parts: a
shorter (few minutes) and less intense preliminary part comprised a decrease
of AL and a negative variation of PC. A longer (about ten minutes) and
more intense main part of the signature comprised an increase of AU and a
positive variation of PC. Measurements from several ground-based
magnetometer networks (210 MM CPMN, CANMOS, CARISMA, GIMA, IMAGE, MACCS,
SuperMAG, THEMIS, TGO) were used to obtain information on the ionospheric
E×B drift. Before the pressure increase, a
configuration typical for the prevailing northward IMF conditions was
observed at high latitudes. The preliminary signature coincided with a pair
of reverse convection vortices, whereas during the main signature, mainly
westward convection was observed at all local time sectors. Afterwards, the
configuration preceding the pressure increase was recovered, but with
slightly enhanced convection. Based on the timing analysis, the existence of
the preliminary signature coincided with the passage of the oblique pressure
front, whereas during the main signature the front was already well past
Earth. The main signature existed during the time the magnetopause was
observed to move. As the position stabilised, also the signature disappeared. |
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