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| Titel |
Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field |
| VerfasserIn |
S. E. Milan, Mark Lester, S. W. H. Cowley, M. Brittnacher |
| 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 ; 18, no. 4 ; Nr. 18, no. 4, S.436-444 |
| Datensatznummer |
250013954
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| Publikation (Nr.) |
 copernicus.org/angeo-18-436-2000.pdf |
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| Zusammenfassung |
We investigate the dayside auroral dynamics
and ionospheric convection during an interval when the interplanetary magnetic
field (IMF) had predominantly a positive Bz component
(northward IMF) but varying By. Polar UVI observations of the
Northern Hemisphere auroral emission indicate the existence of a region of
luminosity near local noon at latitudes poleward of the dayside auroral oval,
which we interpret as the ionospheric footprint of a high-latitude reconnection
site. The large field-of-view afforded by the satellite-borne imager allows an
unprecedented determination of the dynamics of this region, which has not
previously been possible with ground-based observations. The location of the
emission in latitude and magnetic local time varies in response to changes in
the orientation of the IMF; the cusp MLT and the IMF By
component are especially well correlated, the emission being located in the pre-
or post-noon sectors for By < 0 nT or By
> 0 nT, respectively. Simultaneous ground-based observations of the
ionospheric plasma drift are provided by the CUTLASS Finland HF coherent radar.
For an interval of IMF By \approx 0 nT, these convection flow
measurements suggest the presence of a clockwise-rotating lobe cell contained
within the pre-noon dayside polar cap, with a flow reversal closely co-located
with the high-latitude luminosity region. This pattern is largely consistent
with recent theoretical predictions of the convection flow during northward IMF.
We believe that this represents the first direct measurement of the convection
flow at the imaged location of the footprint of the high-latitude reconnection
site.
Key words: Magnetospheric physics (auroral phenomena;
magnetopause · cusp · and boundary layers; plasma convection) |
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