 |
| Titel |
Multiple magnetic dipolarizations observed by THEMIS during a substorm |
| VerfasserIn |
S. P. Duan, Z. X. Liu, J. Liang, Y. C. Zhang, T. Chen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 29, no. 2 ; Nr. 29, no. 2 (2011-02-15), S.331-339 |
| Datensatznummer |
250016971
|
| Publikation (Nr.) |
 copernicus.org/angeo-29-331-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| The magnetic field dipolarization in the vicinity of substorm onset
and during substorm expansion phase during the period of
06:00–06:40 UT on 15 February 2008 is investigated with
observations from multiple probes of THEMIS. It is found that the
magnetic dipolarization at the substorm onset (the onset time was
about 06:14 UT) was not accompanied by obvious magnetic disturbance
and ion bulk speed variation. The magnetic dipolarizations taking
place during the substorm expansion phase observed by
P4~(−10.97, 2.04, −3.03) RE and
P3~(−11.32, 1.15, −3.10) RE were mostly
accompanied by high speed earthward ion bulk flow, but the magnetic
dipolarizations occurring during the substorm expansion phase
observed by P5~(−9.45, 1.07, −2.85) RE were not
accompanied by high speed earthward ion bulk flow. Before substorm
onset THEMIS P3, P4, P5 all observed the Bx component
fluctuation with a period of about 300 s. After substorm onset
earthward high speed ion bulk flow and significant magnetic
disturbances both occurred at P3 and P4 locations. These results
indicate that there is no one-to-one relationship between the
near-Earth magnetic dipolarization and the earthward ion bulk flow.
In particular, the magnetic dipolarization occurring on the
earthward side of the inner near-Earth plasma sheet is not
accompanied by high speed earthward ion bulk flow. The
dipolarization at substorm onset is a local and small scale
phenomenon. There are multiple magnetic dipolarizations occurring
during the substorm expansion phase. The dipolarization process is
very complex and is not simply an MHD process. It is accompanied by
some kinds of plasma instabilities, the plasma sheet azimuthal
expansion not only by earthward ion bulk flow during substorm. A
sharp increase of the AE index does not always give an accurate
substorm onset time for substorm analysis. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|