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| Titel |
GEOTAIL observation of tilted X-line formation during flux transfer events (FTEs) in the dayside magnetospheric boundary layers |
| VerfasserIn |
M. Nowada, T. Sakurai, T. Mukai |
| 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 ; 22, no. 8 ; Nr. 22, no. 8 (2004-09-07), S.2907-2916 |
| Datensatznummer |
250014974
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| Publikation (Nr.) |
 copernicus.org/angeo-22-2907-2004.pdf |
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| Zusammenfassung |
| The magnetic field and plasma structures during two successive crossings of
the subsolar magnetospheric boundary layers (i.e. MagnetoPause Current Layer
(MPCL) and Low-Latitude Boundary Layer (LLBL)) under the southward-dawnward
IMF are examined on the basis of the data obtained by the GEOTAIL spacecraft.
A significant and interesting feature is found, that is, Flux Transfer Events
(FTEs) occur in association with the formation of the tilted X-line. During
the first inbound MPCL/LLBL crossing, the ion velocity enhancement (in
particular, the Vl component negatively increases) can be observed in
association with simultaneous typical bipolar signature (positive followed by
negative) in the Bn component. In addition, a clear D-shaped ion
distribution whose origin is the magnetosheath can also be found in the
dawnward direction. A few minutes later, the satellite experiences outbound
MPCL crossing. The negative enhancement of the Vm component can be
found as well as the positive enhancement of the Vl component. Simultaneously,
a typical bipolar signature with the polarity (negative followed by positive)
opposite that observed in the first encounter can also be observed. The ions
from the magnetosheath flow predominantly in the duskward direction, although
the D-shaped ion distribution cannot be observed. These results indicate that
the satellite initially observes one part of a reconnected flux tube formed
by FTEs whose magnetospheric side is anchored to the Southern Hemisphere. The
ions confined in this partial flux tube are flowing in the south-dawnward
direction. Then, the satellite observes the other part of the reconnected
flux tube whose magnetospheric side is anchored to the Northern Hemisphere.
The ions confined in this flux tube flow dominantly in the north-duskward
direction. Furthermore, it can be considered that the second MPCL crossing is
a direct cut through the diffusion region of FTEs because the LLBL is absent
in the vicinity of the MPCL. On the basis of these results, it can be concluded
that the satellite was passing near the tilted X-line.
The information obtained through this study is expected to be of great use
in discriminating between the anti-parallel (steady-state) reconnection and
tilted X-line models on the dayside MPCL. |
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