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| Titel |
Polar cap flow channel events: spontaneous and driven responses |
| VerfasserIn |
P. E. Sandholt, Y. Andalsvik, C. J. Farrugia |
| 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 ; 28, no. 11 ; Nr. 28, no. 11 (2010-11-05), S.2015-2025 |
| Datensatznummer |
250016907
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| Publikation (Nr.) |
 copernicus.org/angeo-28-2015-2010.pdf |
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| Zusammenfassung |
| We present two case studies of
specific flow channel events appearing at the
dusk and/or dawn polar cap boundary
during passage at Earth of
interplanetary (IP) coronal mass ejections (ICMEs)
on 10 January and 25 July 2004.
The channels of enhanced (>1 km/s) antisunward
convection are documented by SuperDARN radars and dawn-dusk
crossings of the polar cap by the DMSP F13 satellite.
The relationship with Birkeland currents (C1–C2) located poleward of the
traditional R1–R2 currents is demonstrated.
The convection events are manifest in ground magnetic deflections
obtained from the IMAGE (International Monitor for Auroral
Geomagnetic Effects)
Svalbard chain of ground magnetometer stations
located within 71–76° MLAT.
By combining the ionospheric convection data and the ground magnetograms
we are able to study the temporal behaviour of the
convection events.
In the two ICME case studies
the convection events belong to
two different categories, i.e., directly driven and spontaneous
events. In the 10 January case two sharp southward
turnings of the ICME magnetic field excited
corresponding convection events as detected by IMAGE and SuperDARN.
We use this case to determine the ground magnetic signature of
enhanced flow channel events (the NH-dusk/By<0 variant).
In the 25 July case a several-hour-long interval of
steady southwest ICME field (Bz<0; By<0) gave rise to a
long series of
spontaneous convection events as detected by IMAGE when the ground stations
swept through the 12:00–18:00 MLT sector.
From the ground-satellite conjunction on 25 July
we infer the pulsed nature
of the polar cap ionospheric flow channel events in this case.
The typical duration of these convection enhancements
in the polar cap is 10 min. |
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