A Transient Coronal Sigmoid in Active Region NOAA 11909: Build-up Phase, M-class Eruptive Flare, and Associated Fast Coronal Mass Ejection

• Published in: arXiv.org 2021-05
• Main Authors: Kharayat, Hema, Joshi, Bhuwan, Mitra, Prabir K, Manoharan, P K, Monstein, Christian
• Format: Article
• Language: English
• Subjects: Accumulation; Coronal loops; Coronal mass ejection; Disruption; Evolution; Field of view; Magnetic flux; Photosphere; Radio frequency; Soft x rays
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2105.00411

In this article, we investigate the formation and disruption of a coronal sigmoid from the active region (AR) NOAA 11909 on 07 December 2013, by analyzing multi-wavelength and multi-instrument observations. Our analysis suggests that the formation of `transient' sigmoid initiated \(\approx\)1 hour before its eruption through a coupling between two twisted coronal loop systems. A comparison between coronal and photospheric images suggests that the coronal sigmoid was formed over a simple \(\beta\)-type AR which also possessed dispersed magnetic field structure in the photosphere. The line-of-sight photospheric magnetograms also reveal moving magnetic features, small-scale flux cancellation events near the PIL, and overall flux cancellation during the extended pre-eruption phase which suggest the role of tether-cutting reconnection toward the build-up of the flux rope. The disruption of the sigmoid proceeded with a two-ribbon eruptive M1.2 flare (SOL2013-12-07T07:29). In radio frequencies, we observe type III and type II bursts in meter wavelengths during the impulsive phase of the flare. The successful eruption of the flux rope leads to a fast coronal mass ejection (with a linear speed of \(\approx\)1085 km s -1 ) in SOHO/LASCO field-of-view. During the evolution of the flare, we clearly observe typical "sigmoid-to-arcade" transformation. Prior to the onset of the impulsive phase of the flare, flux rope undergoes a slow rise (\(\approx\)15 km s -1 ) which subsequently transitions into a fast eruption (\(\approx\)110 km s -1 ). The two-phase evolution of the flux rope shows temporal associations with the soft X-ray precursor and impulsive phase emissions of the M-class flare, respectively, thus pointing toward a feedback relationship between magnetic reconnection and early CME dynamics.