Development of a Confined Circular-Cum-Parallel Ribbon Flare and Associated Pre-Flare Activity

• Published in: Solar physics 2020-06, Vol.295 (6), Article 75
• Main Authors: Devi, Pooja, Joshi, Bhuwan, Chandra, Ramesh, Mitra, Prabir K., Veronig, Astrid M., Joshi, Reetika
• Format: Article
• Language: English
• Subjects: Astrophysics and Astroparticles; Atmospheric Sciences; Brightening; Configurations; Magnetic fields; Magnetic flux; Magnetic reconnection; Morphology; Observatories; Photosphere; Physics; Physics and Astronomy; Solar activity; Solar activity regions; Solar energy; Solar observatories; Solar physics; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Spine; Sun
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-020-01642-y

We study a complex GOES M1.1 circular ribbon flare and related pre-flare activity on 26 January 2015 [SOL2015-01-26T16:53] in the solar active region NOAA 12268. This flare activity was observed by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The examination of photospheric magnetograms during the extended period, prior to the event, suggests the successive development of a so-called “anemone” type magnetic configuration. The Nonlinear Force Free Field (NLFFF) extrapolation reveals a fan-spine magnetic configuration with the presence of a coronal null-point. We found that the pre-flare activity in the active region starts ≈15 min prior to the main flare in the form of localized bright patches at two locations. A comparison of locations and spatial structures of the pre-flare activity with magnetic configuration of the corresponding region suggests onset of magnetic reconnection at the null-point along with the low-atmosphere magnetic reconnection caused by the emergence and the cancellation of the magnetic flux. The main flare of M1.1 class is characterized by the formation of a well-developed circular ribbon along with a region of remote brightening. Remarkably, a set of relatively compact parallel ribbons formed inside the periphery of the circular ribbon which developed lateral to the brightest part of the circular ribbon. During the peak phase of the flare, a coronal jet is observed at the north-east edge of the circular ribbon, which suggests interchange reconnection between large-scale field lines and low-lying closed field lines. Our investigation suggests a combination of two distinct processes in which ongoing pre-flare null-point reconnection gets further intensified as the confined eruption along with jet activity proceeded from within the circular ribbon region which results to the formation of inner parallel ribbons and corresponding post-reconnection arcade.