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On small active region filaments, fibrils and surges
Stockholm University, Faculty of Science, Department of Astronomy.
2008 (English)In: Advances in Space Research, Vol. 42, no 5, 803-811 p.Article in journal (Refereed) Published
Abstract [en]

High resolution Hα images and magnetograms (0.2 arc s) of an active region were obtained in alternating time series at 42 s cadences using the Swedish 1-m Solar Telescope on 2004 August 21. The Hα filtergrams reveal an active region filament and surges consisting of thread-like structures which have widths similar to the widths of chromospheric fibrils, both recorded down to the resolution limit in the best images. All observed structures in the active region appear highly dynamic. Fibrils show counterstreaming strongly resembling the counterstreaming threads in filaments. Streaming, along the threads of surges extending more than 10 arc s, is higher in speed (˜20 km s‑1) than in the filament and fibrils and appears to flow independently over and above the chromospheric fibrils. Blue shifts seen in the Hα Dopplergrams confirm the outward mass motion of the surges. However, in at least one case, we also see simultaneous downflows from the same site but in the opposite direction and downward toward the chromosphere. We suggest that the site between these two outward and downward flows identifies the place where magnetic reconnection could occur and thereby cause of the surge. This appears to imply that the reconnection site is in the high chromosphere or low corona.

Place, publisher, year, edition, pages
2008. Vol. 42, no 5, 803-811 p.
URN: urn:nbn:se:su:diva-18318DOI: doi:10.1016/j.asr.2007.05.052OAI: diva2:184841
Available from: 2009-01-25 Created: 2009-01-25 Last updated: 2011-01-10Bibliographically approved

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van Noort, Michiel
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