Unwinding motion of a twisted active-region filament

Abstract

To better understand the structures of active-region filaments and the eruption process, we study an active-region filament eruption in active region NOAA 11082 in detail on June 22, 2010. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament is consisted of twisted magnetic field lines. The total twist of the filament is at least 5$\pi$ obtained by using time slice method. According to the morphology change during the filament eruption, it is found that the active-region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.

26 pages,11 figures, accepted for publication in ApJ

References in corpus (8)

• Torus instability
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• Flux rope proxies and fan-spine structures in active region NOAA 11897
• Direct Observation of A Large-scale CME Flux Rope Event Arising from an Unwinding Coronal Jet
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• Untwisting and Disintegration of a Solar Filament Associated with Photospheric Flux Cancellation
• Failed Solar Eruption of A Multi-thermal Flux Rope
• Spectral Characteristics of a Rotating Solar Prominence in Multiple Wavelengths
• Signatures of Untwisting Magnetic Field in a Small Emerging Bipole in the Solar Photosphere
• The Observations of Magnetic Reconnection During the Interaction Process of Two Active Region Filaments
• Multi-wavelength and Dual-perspective Observations of Eruption and Untwisting of Two Homologous Magnetic Flux Ropes