 |
| Titel |
Stationary magnetospheric convection on November 24, 1981. 1. A case study of "pressure gradient/minimum-B" auroral arc generation |
| VerfasserIn |
Y. I. Galperin, J. M. Bosqued |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 17, no. 3 ; Nr. 17, no. 3, S.358-374 |
| Datensatznummer |
250013692
|
| Publikation (Nr.) |
 copernicus.org/angeo-17-358-1999.pdf |
|
|
|
|
|
| Zusammenfassung |
We present two case studies in the night and
evening sides of the auroral oval, based on plasma and field measurements made
at low altitudes by the AUREOL-3 satellite, during a long period of stationary
magnetospheric convection (SMC) on November 24, 1981. The basic feature of both
oval crossings was an evident double oval pattern, including (1) a weak arc-type
structure at the equatorial edge of the oval/polar edge of the diffuse auroral
band, collocated with an upward field-aligned current (FAC) sheet of \sim1.0 µA
m-2, (2) an intermediate region of weaker precipitation within the
oval, (3) a more intense auroral band at the polar oval boundary, and (4) polar
diffuse auroral zone near the polar cap boundary. These measurements are
compared with the published magnetospheric data during this SMC period,
accumulated by Yahnin et al. and Sergeev et al., including a
semi-empirical radial magnetic field profile BZ in the
near-Earth neutral sheet, with a minimum at about 10-14 RE.
Such a radial BZ profile appears to be very similar to that
assumed in the "minimum- B/cross-tail line current" model by
Galperin et al. (GVZ92) as the "root of the arc", or the arc
generic region. This model considers a FAC generator mechanism by
Grad-Vasyliunas-Boström-Tverskoy operating in the region of a narrow magnetic
field minimum in the near-Earth neutral sheet, together with the concept of ion
non-adiabatic scattering in the "wall region". The generated upward
FAC branch of the double sheet current structure feeds the steady auroral
arc/inverted-V at the equatorial border of the oval. When the semi-empirical BZ
profile is introduced in the GVZ92 model, a good agreement is found between the
modelled current and the measured characteristics of the FACs associated with
the equatorial arc. Thus the main predictions of the GVZ92 model concerning the
"minimum-B" region are consistent with these data, while some
small-scale features are not reproduced. Implications of the GVZ92 model are
discussed, particularly concerning the necessary conditions for a substorm onset
that were not fulfilled during the SMC period.
Key words. Magnetospheric physics (auroral phenomena;
magnetospheric configuration and dynamics; plasma sheet). |
| |
|
| Teil von |
|
|
|
|
|
|
|
|