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| Titel |
Magnetic Field and Plasma Responses in the Near-Earth Magnetotail and Magnetospheric Boundary Layer During an Encounter of Heliospheric Current Sheet |
| VerfasserIn |
Motoharu Nowada, Ching-Huei Lin, Sui-Yan Fu, Zu-Yin Pu, Howard J. Singer, Vassilis Angelopoulos, Charles W. Carlson, Hans-Ulrich Auster |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047432
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| Zusammenfassung |
| We examined responses for the magnetic field and plasma in the dawn and duskside
near-earth magnetotail regions and magnetospheric boundary layer due to an encounter of
Heliospheric Current Sheet (HCS) indicated as a sharp discontinuity in the Bx component of
the Interplanetary Magnetic Field (IMF) without striking variation of the solar wind dynamic
pressure and the polarity change of the IMF-Bz component. In this study, the magnetic field
and plasma data obtained from THEMIS, Cluster, GOES-11 and -12 to investigate the
magnetic field and plasma responses in the near-earth magnetotail region and magnetospheric
boundary layer, and those taken from ACE and GEOTAIL to monitor associated solar wind
conditions are utilized. Simultaneous geomagnetic field variations at high-latitude ground
observatories were also examined. When HCS encountered with the magnetosphere,
THEMIS-D, -E and -A observed the abrupt and transient magnetic field and plasma
variations in the dawnside near-earth magnetotail, but the aspects and duration for
these variations observed by between THEMIS-D, -E and -A were totally different.
Although Cluster was oppositely located in the duskside magnetotail, only much
smaller magnetic field perturbations were seen. Simultaneous enhancement of the
north-south magnetic field component (Bz) associated with dipolarization, and negative
bay variations accompanied by the Pi 2 waves were observed by GOES-11, -12,
which were located at the pre-midnight and pre-dawn sectors, respectively, and the
ground observatories. THEMIS-C, which was located in the magnetosheath just
adjacent to the dawnside magnetopause and near THEMIS-A, experienced the single
and multiple magnetopause crossings. This result indicates that the magnetopause
surface waves were generated, although simultaneous solar wind conditions had
been stable. Compared the magnetic field variations of THEMIS-A with those of
THEMIS-C, the peaks of the abrupt and transient magnetic field variations observed
by THEMIS-A were almost consistent with the magnetic field variation levels of
THEMIS-C. Based on these observational results, it suggests that the abrupt and
transient magnetic field and plasma variations observed by THEMIS-D and -E were
direct phenomena caused by substorm, and those by THEMIS-A and the single
and multiple magnetopause crossings experienced by THEMIS-C were caused by
the magnetopause undulations due to substorm-associated inner-magnetospheric
configuration changes. Furthermore, this substorm due to an encounter of HCS
occurred locally because the magnetic field and plasma variations observed by
THEMIS were localized upon the dawnside near-earth magnetotail region and their
durations were also short-lived. The results obtained through this study emphasize that
clear disturbances in the inner-magnetosphere can be brought by only one solar
wind parameter’s striking variation, although the solar wind conditions do not have
significant variations that will make the magnetospheric condition change dramatically,
such as an abrupt or long-term variation of the solar wind dynamic pressure, and
an encounter of the impulsive or large southward (northward) IMF-Bz structure. |
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