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| Titel |
Electric current and magnetic field geometry in flapping magnetotail current sheets |
| VerfasserIn |
A. Runov, V. A. Sergeev, W. Baumjohann, R. Nakamura, S. Apatenkov, Y. Asano, M. Volwerk, Z. Vörös, T. L. Zhang, A. Petrukovich, A. Balogh, J.-A. Sauvaud, B. Klecker, H. Rème |
| 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 ; 23, no. 4 ; Nr. 23, no. 4 (2005-06-03), S.1391-1403 |
| Datensatznummer |
250015231
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1391-2005.pdf |
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| Zusammenfassung |
| Using four-point magnetic field measurements by the Cluster
spacecraft, we statistically analyze the magnetic field and
electric current configurations during rapid crossings of the
current sheet observed in July-October 2001 at geocentric
distances of 19 RE.
The database includes 78 crossings, specially selected to
apply multi-point data analysis techniques to calculate
vector derivatives.
Observed bipolar variations of jz, often with | jz |>jy,
indicate that the
electric currents follow kinks of the current sheet. The current
density varies between 5-25nA/m2. The half-thickness
of the current sheet during flapping varies over a wide range,
from 1 to 20 ion thermal gyroradii (Lcp), calculated
from average temperature and lobe magnetic field for each
crossing). We found no relationship between the tilt angle of the
current sheet normal and the half-thickness. In 68 cases the
magnetic field curvature vector has a positive (earthward)
X-component. Ten cases with a negative (tailward) curvature,
associated with reconnection, were detected within
0<YGSM<7 RE.
The minimum curvature radii vary mainly between 1 and
10 Lcp, and the adiabaticity parameter κ≤1 for 73% of the
events. The electric current density
during flapping is often off-central, i.e. the main current
density is shifted from the neutral sheet (| Bx |<5nT) to
the Northern or Southern Hemisphere. This is most likely a
temporal effect related to the flapping.
The analysis shows that the flapping motion of the current
sheet is associated with kink-like waves on the sheet
surface. The kink fronts, tilted in the Y-Z
plane, moved toward dawn in the morning half and toward dusk
in the evening half of the magnetotail. |
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