 |
| Titel |
A quantitative study of magnetospheric magnetic field line deformation by a two-loop substorm current wedge |
| VerfasserIn |
A. V. Nikolaev, V. A. Sergeev, N. A. Tsyganenko, M. V. Kubyshkina, H. Opgenoorth, H. Singer, V. Angelopoulos |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 33, no. 4 ; Nr. 33, no. 4 (2015-04-29), S.505-517 |
| Datensatznummer |
250121192
|
| Publikation (Nr.) |
 copernicus.org/angeo-33-505-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Substorm current wedge (SCW) formation is associated with global magnetic
field reconfiguration during substorm expansion. We combine a two-loop model
SCW (SCW2L) with a background magnetic field model to investigate distortion
of the ionospheric footpoint pattern in response to changes of different
SCW2L parameters. The SCW-related plasma sheet footprint shift results in
formation of a pattern resembling an auroral bulge, the poleward expansion
of which is controlled primarily by the total current in the region 1 sense
current loop (I1). The magnitude of the footprint latitudinal shift may
reach ∼ 10° corrected geomagnetic latitude (CGLat) during strong substorms (I1= 2 MA). A strong helical magnetic field around the field-aligned current
generates a surge-like region with embedded spiral structures, associated
with a westward traveling surge (WTS) at the western end of the SCW. The
helical field may also contribute to rotation of the ionospheric projection
of narrow plasma streams (auroral streamers). Other parameters, including
the total current in the second (region 2 sense) loop, were found to be of
secondary importance. Analyzing two consecutive dipolarizations on 17 March
2010, we used magnetic variation data obtained from a dense midlatitude
ground network and several magnetospheric spacecraft, as well as the
adaptive AM03 model, to specify SCW2L parameters, which allowed us to
predict the magnitude of poleward auroral expansion. Auroral observations
made during the two substorm activations demonstrate that the SCW2L combined
with the AM03 model nicely describes the azimuthal progression and the
observed magnitude of the auroral expansion. This finding indicates that the
SCW-related distortions are responsible for much of the observed global
development of bright auroras. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|