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| Titel |
Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study |
| VerfasserIn |
S. E. Milan, Mark Lester, S. W. H. Cowley, J. Moen, P. E. Sandholt, C. J. Owen |
| 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. 2 ; Nr. 17, no. 2, S.159-172 |
| Datensatznummer |
250013668
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| Publikation (Nr.) |
 copernicus.org/angeo-17-159-1999.pdf |
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| Zusammenfassung |
The dynamics of the cusp region and post-noon
sector for an interval of predominantly IMF By, Bz
< 0 nT are studied with the CUTLASS Finland coherent HF radar, a
meridian-scanning photometer located at Ny Ålesund, Svalbard, and a meridional
network of magnetometers. The scanning mode of the radar is such that one beam
is sampled every 14 s, and a 30° azimuthal sweep is completed every 2 minutes,
all at 15 km range resolution. Both the radar backscatter and red line (630 nm)
optical observations are closely co-located, especially at their equatorward
boundary. The optical and radar aurora reveal three different behaviours which
can interchange on the scale of minutes, and which are believed to be related to
the dynamic nature of energy and momentum transfer from the solar wind to the
magnetosphere through transient dayside reconnection. Two interpretations of the
observations are presented, based upon the assumed location of the open/closed
field line boundary (OCFLB). In the first, the OCFLB is co-located with
equatorward boundary of the optical and radar aurora, placing most of the
observations on open field lines. In the second, the observed aurora are
interpreted as the ionospheric footprint of the region 1 current system, and the
OCFLB is placed near the poleward edge of the radar backscatter and visible
aurora; in this interpretation, most of the observations are placed on closed
field lines, though transient brightenings of the optical aurora occur on open
field lines. The observations reveal several transient features, including
poleward and equatorward steps in the observed boundaries, "braiding"
of the backscatter power, and 2 minute quasi-periodic enhancements of the plasma
drift and optical intensity, predominantly on closed field lines.
Key words. Ionosphere (auroral ionosphere; plasma
convection) · Magnetospheric physics (magnetopause · cusp · and boundary
layers) |
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