Abstract Details
| Name: Prabir Kumar Mitra Affiliation: Physical Research Laboratory Conference ID: ASI2018_1628 Title : Flux Rope Eruption From a Sigmoid Active Region: Triggering Mechanism and Large-scale Magnetic Reconnection Authors and Co-Authors : Bhuwan Joshi, Physical Research Laboratory Abstract Type : Poster Abstract Category : Sun and the Solar System Abstract : Coronal sigmoids are complex active regions that exhibit enhanced soft X-ray or EUV coronal emission from a system of twisted coronal loops that overall form an S (or inverse S) shaped morphology[1]. It is well established that sigmoidal active regions tend to produce frequent coronal mass ejections (CMEs) over non-sigmoidal ones[2]. Our understanding regarding the formation stages of coronal sigmoids and triggering of eruption from such magnetically complex regions is still very limited. In this paper, we present a comprehensive multi-wavelength investigation of the onset of flux rope eruption and subsequent reconnection-driven large-scale phenomena from sigmoid active region NOAA 12371 on 2015 June 21. For the purpose, we have analyzed solar observations taken from SDO[3], GOES[4], and RHESSI[5]. The SDO/AIA images at 94 A channel reveals that flux rope underwent eruption in two distinct phases that led to two successive, well-separated M-class flares. LASCO CME observations show that the successful eruption of the flux rope eventually produced a large halo CME. The build-up phase of the coronal sigmoid is characterized by striking magnetic activities in the photosphere which includes counter clockwise rotation of a negative polarity region along with adjacent moving magnetic features. The flux rope activation occurred within a compact coronal volume that displayed enhanced EUV emission. Compact brightenings observed in multi-channel EUV images in the vicinity of photospheric neutral line during the activation phase along with flux cancellation suggest tether-cutting[6] reconnection to be the driving mechanism for the eruption onset. The rapid expansion of the flux rope led to the first M-class flare with relatively less spatial extents. The second flare presents extended chromospheric ribbons and larger loop structures. The multi-wavelength observations further suggest interactions of the expanding flux rope with overlying coronal loops at higher altitude caused the second M-class flare. |