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| Titel |
High-latitude observations of impulse-driven ULF pulsations in the ionosphere and on the ground |
| VerfasserIn |
F. W. Menk, T. K. Yeoman, D. M. Wright, Mark Lester, F. Honary |
| 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 ; 21, no. 2 ; Nr. 21, no. 2, S.559-576 |
| Datensatznummer |
250014574
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| Publikation (Nr.) |
 copernicus.org/angeo-21-559-2003.pdf |
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| Zusammenfassung |
We report the
simultaneous observation of 1.6–1.7 mHz pulsations in the ionospheric
F-region with the CUTLASS bistatic HF radar and an HF Doppler sounder, on the
ground with the IMAGE and SAMNET magnetometer arrays, and in the upstream solar
wind. CUTLASS was at the time being operated in a special mode optimized for
high resolution studies of ULF waves. A novel use is made of the ground returns
to detect the ionospheric signature of ULF waves. The pulsations were initiated
by a strong, sharp decrease in solar wind dynamic pressure near 09:28 UT on 23
February 1996, and persisted for some hours. They were observed with the
magnetometers over 20° in latitude, coupling to a field line resonance near
72° magnetic latitude. The magnetic pulsations had azimuthal m numbers ~ -2,
consistent with propagation away from the noon sector. The radars show
transient high velocity flows in the cusp and auroral zones, poleward of the
field line resonance, and small amplitude 1.6–1.7 mHz F-region oscillations
across widely spaced regions at lower latitudes. The latter were detected in
the radar ground scatter returns and also with the vertical incidence Doppler
sounder. Their amplitude is of the order of ± 10 ms-1. A similar
perturbation frequency was present in the solar wind pressure recorded by the
WIND spacecraft. The initial solar wind pressure decrease was also associated
with a decrease in cosmic noise absorption on an imaging riometer near 66°
magnetic latitude. The observations suggest that perturbations in the solar
wind pressure or IMF result in fast compressional mode waves that propagate
through the magnetosphere and drive forced and resonant oscillations of
geomagnetic field lines. The compressional wave field may also stimulate
ionospheric perturbations. The observations demonstrate that HF radar ground
scatter may contain important information on small-amplitude features,
extending the scope and capability of these radars to track features in the
ionosphere.
Key words. Ionosphere
(Ionosphere-magnetosphere interactions; ionospheric disturbances) –
Magnetospheric physics (MHD waves and instabilities) |
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