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| Titel |
The magnetosphere under weak solar wind forcing |
| VerfasserIn |
C. J. Farrugia, A. Grocott, P. E. Sandholt, S. W. H. Cowley, Y. Miyoshi, F. J. Rich, V. K. Jordanova, R. B. Torbert, A. Sharma |
| 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 ; 25, no. 1 ; Nr. 25, no. 1 (2007-02-01), S.191-205 |
| Datensatznummer |
250015771
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| Publikation (Nr.) |
 copernicus.org/angeo-25-191-2007.pdf |
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| Zusammenfassung |
| The Earth's magnetosphere was very strongly disturbed during the passage of
the strong shock and the following interacting ejecta on 21–25 October 2001.
These disturbances included two
intense storms (Dst*≈−250 and −180 nT, respectively). The cessation of this
activity at the start of 24 October ushered in a peculiar
state of the magnetosphere which lasted for about
28 h and which we discuss in this paper. The interplanetary field was dominated by the
sunward component [B=(4.29±0.77, −0.30±0.71, 0.49±0.45) nT].
We analyze global indicators of geomagnetic disturbances, polar cap precipitation,
ground magnetometer records,
and ionospheric convection as obtained from SuperDARN radars.
The state of the magnetosphere is characterized by the following features: (i) generally weak
and patchy (in time) low-latitude dayside reconnection or reconnection poleward of
the cusps; (ii) absence of substorms; (iii) a monotonic recovery from the previous
storm activity (Dst corrected for magnetopause currents decreasing from ~−65 to
~−35 nT),
giving an unforced decreased of ~1.1 nT/h; (iv) the probable absence of viscous-type
interaction originating from the Kelvin-Helmholtz (KH) instability;
(v) a cross-polar cap potential of just 20–30 kV; (vi) a persistent,
polar cap region containing (vii) very weak, and sometimes absent, electron
precipitation and no systematic inter-hemisphere asymmetry.
Whereas we therefore infer the presence of a moderate amount of open flux,
the convection is generally weak and patchy, which we ascribe to the lack of solar
wind driver. This magnetospheric state approaches that
predicted by Cowley and Lockwood (1992)
but has never yet been observed. |
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