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Slow rise and partial eruption of a double-decker filament. I. observations and interpretation

  • We study an active-region dextral filament that was composed of two branches separated in height by about 13 Mm, as inferred from three-dimensional reconstruction by combining SDO and STEREO-B observations. This "double-decker" configuration sustained for days before the upper branch erupted with a GOES-class M1.0 flare on 2010 August 7. Analyzing this evolution, we obtain the following main results. (1) During the hours before the eruption, filament threads within the lower branch were observed to intermittently brighten up, lift upward, and then merge with the upper branch. The merging process contributed magnetic flux and current to the upper branch, resulting in its quasi-static ascent. (2) This transfer might serve as the key mechanism for the upper branch to lose equilibrium by reaching the limiting flux that can be stably held down by the overlying field or by reaching the threshold of the torus instability. (3) The erupting branch first straightened from a reverse S shape that followed the polarity inversion line and thenWe study an active-region dextral filament that was composed of two branches separated in height by about 13 Mm, as inferred from three-dimensional reconstruction by combining SDO and STEREO-B observations. This "double-decker" configuration sustained for days before the upper branch erupted with a GOES-class M1.0 flare on 2010 August 7. Analyzing this evolution, we obtain the following main results. (1) During the hours before the eruption, filament threads within the lower branch were observed to intermittently brighten up, lift upward, and then merge with the upper branch. The merging process contributed magnetic flux and current to the upper branch, resulting in its quasi-static ascent. (2) This transfer might serve as the key mechanism for the upper branch to lose equilibrium by reaching the limiting flux that can be stably held down by the overlying field or by reaching the threshold of the torus instability. (3) The erupting branch first straightened from a reverse S shape that followed the polarity inversion line and then writhed into a forward S shape. This shows a transfer of left-handed helicity in a sequence of writhe-twist-writhe. The fact that the initial writhe is converted into the twist of the flux rope excludes the helical kink instability as the trigger process of the eruption, but supports the occurrence of the instability in the main phase, which is indeed indicated by the very strong writhing motion. (4) A hard X-ray sigmoid, likely of coronal origin, formed in the gap between the two original filament branches in the impulsive phase of the associated flare. This supports a model of transient sigmoids forming in the vertical flare current sheet. (5) Left-handed magnetic helicity is inferred for both branches of the dextral filament. (6) Two types of force-free magnetic configurations are compatible with the data, a double flux rope equilibrium and a single flux rope situated above a loop arcade.show moreshow less

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Metadaten
Author:Rui Liu, Bernhard Kliem, Tibor Toeroek, Chang Liu, Viacheslav S. Titov, Roberto Lionello, Jon A. Linker, Haimin Wang
DOI:https://doi.org/10.1088/0004-637X/756/1/59
ISSN:0004-637X (print)
Parent Title (English):The astrophysical journal : an international review of spectroscopy and astronomical physics
Publisher:IOP Publ. Ltd.
Place of publication:Bristol
Document Type:Article
Language:English
Year of first Publication:2012
Year of Completion:2012
Release Date:2017/03/26
Tag:Sun: coronal mass ejections (CMEs); Sun: filaments, prominences; Sun: flares
Volume:756
Issue:1
Pagenumber:14
Funder:Thousand Young Talents Program of China; NSFC [41131065, 41121003]; 973 key project [2011CB811403]; CAS Key Research Program [KZZD-EW-01-4]; fundamental research funds for the central universities [WK2080000031]; NASA [NNX08-AJ23G, NNX08-AQ90G]; NSF [ATM-0849453, ATM-0819662]; DFG; STFC; NASA's HTP program; NASA's LWS program; NASA's SRT program; CISM (an NSF Science and Technology Center); Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences [KLSA201201]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert