Sunspot splitting triggering an eruptive flare

Abstract

We investigate how the splitting of the leading sunspot and associated flux emergence and cancellation in active region NOAA 11515 caused an eruptive M5.6 flare on 2012 July 2. Our study employs multi-wavelength observations from HMI, AIA and ChroTel. Emerging flux formed a neutral line ahead of the leading sunspot and new satellite spots. The sunspot splitting caused a long-lasting flow toward this neutral line, where a filament formed. Further flux emergence, partly of mixed-polarity, as well as episodes of flux cancellation occurred repeatedly at the neutral line. Following a nearby C-class precursor flare with signs of interaction with the filament, the filament erupted nearly simultaneously with the onset of the M5.6 flare and evolved into a coronal mass ejection. The sunspot stretched without forming a light bridge, splitting unusually fast (within about a day, complete approximately 6 hours after the eruption) in two nearly equal parts. The front part separated strongly from the active region to approach the neighbouring active region where all its coronal magnetic connections were rooted. It also rotated rapidly (by 4.9 degree/hr) and caused significant shear flows at its edge. The eruption resulted from a complex sequence of processes in the (sub-)photosphere and corona. The persistent flows toward the neutral line likely caused the formation of a flux rope which held the filament. These flows and their associated flux cancellation, the emerging flux, and the precursor flare all contributed to the destabilization of the flux rope. We interpret the sunspot splitting as the separation of two flux bundles differently rooted in the convection zone and only temporarily joined in the spot. This explains the rotation as continued rise of the separating flux and implies that at least this part of the sunspot was still connected to its roots deep in the convection zone.

Accepted for publication in A&A :16 pages, 14 figures

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Cited by in corpus (16)

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• Triggering Process of the X1.0 Three-ribbon Flare in the Great Active Region NOAA 12192
• Direct Observation of A Large-scale CME Flux Rope Event Arising from an Unwinding Coronal Jet
• The formation of an atypical sunspot light bridge as a result of large-scale flux emergence
• Non-potential field formation in the X-shaped quadrupole magnetic field configuration
• Untwisting and Disintegration of a Solar Filament Associated with Photospheric Flux Cancellation
• Background-subtracted Solar Activity Maps
• Evaluation of Applicability of a Flare Trigger Model based on Comparison of Geometric Structures
• Magnetohydrodynamics evolution of three-dimensional magnetic null in NOAA active region 11515 initiated using non-force-free field extrapolation
• Calibration of full-disk He I 10830 Å filtergrams of the Chromospheric Telescope
• The configuration and failed eruption of a complex magnetic flux rope above a δ sunspot region
• Homologous flaring activity over a sunspot light bridge in an emerging active region
• Multi-wavelength and Dual-perspective Observations of Eruption and Untwisting of Two Homologous Magnetic Flux Ropes
• Design of an adaptable Stokes polarimeter for exploring chromospheric magnetism