Formation and eruption of sigmoidal structure from a weak field region of NOAA 11942

Abstract

Using observations from Solar Dynamics Observatory, we studied an interesting example of a sigmoid formation and eruption from small-scale flux canceling regions of active region (AR) 11942. Analysis of HMI and AIA observations infer that initially the AR is compact and bipolar in nature, evolved to sheared configuration consisting of inverse J-shaped loops hosting a filament channel over a couple of days. By tracking the photospheric magnetic features, shearing and converging motions are observed to play a prime role in the development of S-shaped loops and further flux cancellation leads to tether-cutting reconnection of J-loops. This phase is co-temporal with the filament rise motion followed by sigmoid eruption at 21:32 UT on January 6. The flux rope rises in phases of slow (v${}_{avg}$ = 26 km~s${}^{-1}$) and fast (a${}_{avg}$= 55 ms${}^{-2}$) rise motion categorizing the CME as slow with an associated weak C1.0 class X-ray flare. The flare ribbon separation velocity peaks at around peak time of the flare at which maximum reconnection rate (2.14 Vcm${}^{-1}$) occurs. Further, the EUV light-curves of 131, 171Å~have delayed peaks of 130 minutes compared to 94Å~and is explained by differential emission measure. Our analysis suggests that the energy release is proceeded in a much long time duration, manifesting the onset of filament rise and eventual eruption driven by converging and canceling flux in the photosphere. Unlike strong eruption events, the observed slow CME and weak flare are indications of slow runway tether-cutting reconnection where most of the sheared arcade is relaxed during the extended post phase of the eruption.

Accepted for Publication in The Astrophysical journal on 19 February, 2019. It has 17 pages including 12 figures

References in corpus (13)

• Torus instability
• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches
• Ideal kink instability of a magnetic loop equilibrium
• Observation of An Evolving Magnetic Flux Rope Prior To and During A Solar Eruption
• Photospheric flux cancellation and associated flux rope formation and eruption
• Sigmoid-to-Flux-Rope Transition Leading to A Loop-Like Coronal Mass Ejection
• Flux Rope Formation Preceding Coronal Mass Ejection Onset
• Catastrophe versus instability for the eruption of a toroidal solar magnetic flux rope
• On the origin of the Extreme-Ultraviolet late phase of solar flares
• Electric-Current Neutralization, Magnetic Shear, and Eruptive Activity in Solar Active Regions
• Initiation and Eruption Process of Magnetic Flux Rope from Solar Active Region NOAA 11719 to Earth Directed-CME
• Successive Homologous Coronal Mass Ejections driven by shearing and converging motions in solar active region NOAA 12371
• Two Energy Release Processes for CMEs: MHD Catastrophe and Magnetic Reconnection

Cited by in corpus (4)

• Observational Analysis on the Early Evolution of a CME Flux-rope: Pre-flare reconnection and Flux-rope's Footpoint Drift
• A Transient Coronal Sigmoid in Active Region NOAA 11909: Build-up Phase, M-class Eruptive Flare, and Associated Fast Coronal Mass Ejection
• Formation and Eruption of a Mini-sigmoid Originating in Coronal Hole
• Magnetic imprints of eruptive and non-eruptive Solar flares as observed by Solar Dynamics Observatory