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| Titel |
Magnetic local time, substorm, and particle precipitation-related variations in the behaviour of SuperDARN Doppler spectral widths |
| VerfasserIn |
M. L. Parkinson, G. Chisham, M. Pinnock, P. L. Dyson, J. C. Devlin |
| 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 ; 22, no. 12 ; Nr. 22, no. 12 (2004-12-22), S.4103-4122 |
| Datensatznummer |
250015077
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| Publikation (Nr.) |
 copernicus.org/angeo-22-4103-2004.pdf |
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| Zusammenfassung |
Super Dual Auroral Radar Network (DARN) radars often
detect a distinct transition in line-of-sight Doppler velocity spread, or
spectral width, from <50ms–1 at lower latitude to >200ms–1 at higher latitude. They also detect a similar boundary, namely the range at
which ionospheric scatter with large spectral width suddenly commences
(i.e. without preceding scatter with low spectral width). The location and
behaviour of the spectral width boundary (SWB) (and scatter boundary) and
the open-closed magnetic field line boundary (OCB) are thought to be closely
related. The location of the nightside OCB can be inferred from the poleward
edge of the auroral oval determined using energy spectra of precipitating
particles measured on board Defence Meteorology Satellite Program (DMSP)
satellites. Observations made with the Halley SuperDARN radar (75.5° S,
26.6° W, geographic; –62.0°Λ) and the Tasman International
Geospace Environment Radar (TIGER) (43.4° S, 147.2° E; –54.5°Λ)
are used to compare the location of the SWB with the
DMSP-inferred OCB during 08:00 to 22:00 UT on 1 April 2000. This study interval was
chosen because it includes several moderate substorms, whilst the Halley
radar provided almost continuous high-time resolution measurements of the
dayside SWB location and shape, and TIGER provided the same in the nightside
ionosphere. The behaviour of the day- and nightside SWB can be understood
in terms of the expanding/contracting polar cap model of high-latitude
convection change, and the behaviour of the nightside SWB can also be
organised according to substorm phase. Previous comparisons with DMSP OCBs
have proven that the radar SWB is often a reasonable proxy for the OCB from dusk
to just past midnight (Chisham et al., 2004). However, the present case
study actually suggests that the nightside SWB is often a better proxy for the
poleward edge of Pedersen conductance enhanced by hot particle precipitation
in the auroral zone. Simple modeling implies that the large spectral widths must
be caused by ~10-km scale velocity fluctuations.
Key words. Ionosphere (auroral ionosphere; ionospheremagnetosphere
interactions) – Magnetospheric physics
(storms and substorms) |
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