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| Titel |
Stationary magnetospheric convection on November 24, 1981. 2. Small-scale structures in the dayside cusp/cleft |
| VerfasserIn |
Y. I. Galperin, J. M. Bosqued, R. A. Kovrazhkin, A. G. Yahnin |
| 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 ; 17, no. 3 ; Nr. 17, no. 3, S.375-388 |
| Datensatznummer |
250013693
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| Publikation (Nr.) |
 copernicus.org/angeo-17-375-1999.pdf |
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| Zusammenfassung |
A case study of the dayside cusp/cleft region
during an interval of stationary magnetospheric convection (SMC) on November,
24, 1981 is presented, based on detailed measurements made by the AUREOL-3
satellite. Layered small-scale field-aligned current sheets, or loops,
superimposed to a narrow V-shaped ion dispersion structure, were observed just
equatorward from the region of the "cusp proper". The equatorward
sheet was accompanied by a very intense and short (less than 1 s) ion intensity
spike at 100 eV. No major differences were noted of the characteristics of the
LLBL, or "boundary cusp", and plasma mantle precipitation during this
SMC period from those typical of the cusp/cleft region for similar IMF
conditions. Simultaneous NOAA-6 and NOAA-7 measurements described in Despirak et
al. were used to estimate the average extent of the "cusp proper"
(defined by dispersed precipitating ions with the energy flux exceeding 10-3
erg cm-2 s-1) during the SMC period, as ~0.73° ILAT
width, 2.6-3.4 h in MLT, and thus the recently merged magnetic flux, 0.54-0.70
× 107 Wb. This, together with the average drift velocity across the
cusp at the convection throat, ~0.5 km s-1, allowed to evaluate
the cusp merging contribution to the total cross-polar cap potential difference,
~33.8-43.8 kV. It amounts to a quite significant part of the total
cross-polar cap potential difference evaluated from other data. A
"shutter" scenario is suggested for the ion beam injection/penetration
through the stagnant plasma region in the outer cusp to explain the pulsating
nature of the particle injections in the low- and medium-altitude cusp region.
Key words. Magnetospheric physics (current systems;
magnetopause · cusp · and boundary layers; solar wind-magnetosphere
interactions). |
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