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| Titel |
Impact of solar wind depression on the dayside magnetosphere under northward interplanetary magnetic field |
| VerfasserIn |
S. Baraka, L. Ben-Jaffel |
| 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 (2011-01-05), S.31-46 |
| Datensatznummer |
250016945
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| Publikation (Nr.) |
 copernicus.org/angeo-29-31-2011.pdf |
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| Zusammenfassung |
| We present a follow up study of the sensitivity of the Earth's magnetosphere to solar
wind activity using a particles-in-cell model (Baraka and Ben Jaffel, 2007), but
here during northward Interplanetary Magnetic Field (IMF). The formation of the
magnetospheric cavity and its elongation around the planet is obtained with the
classical structure of a magnetosphere with parallel lobes. An impulsive
disturbance is then applied to the system by changing the bulk velocity of the
solar wind to simulate a decrease in the solar wind dynamic pressure followed
by its recovery. In response to the imposed drop in the solar wind velocity,
a gap (abrupt depression) in the incoming solar wind plasma appears moving
toward the Earth. The gap's size is a ~15 RE and is comparable
to the sizes previously obtained for both Bz<0 and Bz=0.
During the initial phase of the disturbance along the x-axis, the dayside
magnetopause (MP) expands slower than the previous cases of IMF orientations
as a result of the abrupt depression. The size of the MP expands nonlinearly
due to strengthening of its outer boundary by the northward IMF. Also,
during the initial 100 Δt, the MP shrank down from 13.3 RE
to ~9.2 RE before it started expanding, a phenomenon that was
also observed for southern IMF conditions but not during the no IMF case.
As soon as they felt the solar wind depression, cusps widened at high
altitude while dragged in an upright position. For the field's topology,
the reconnection between magnetospheric and magnetosheath fields is clearly
observed in both the northward and southward cusps areas. Also, the tail region
in the northward IMF condition is more confined, in contrast to the fishtail-shape
obtained in the southward IMF case. An X-point is formed in the tail at ~110 RE
compared to ~103 RE and ~80 RE for Bz=0 and
Bz<0, respectively. Our findings are consistent with existing reports
from many space observatories (Cluster, Geotail, Themis, etc.) for which
predictions are proposed to test furthermore our simulation technique. |
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