Multiwavelength Observations of a Flux Rope Formation by Series of Magnetic Reconnection in the Chromosphere

Abstract

Using high-resolution observations from the 1.6 m New Solar Telescope (NST) operating at the Big Bear Solar Observatory (BBSO), we report direct evidence of merging/reconnection of cool H$\alpha$ loops in the chromosphere during two homologous flares (B- and C-class) caused by a shear motion at the footpoint of two loops. The reconnection between these loops caused the formation of an unstable flux rope which showed counterclockwise rotation. The flux rope could not reach the height of torus instability and failed to form a coronal mass ejection. The HMI magnetograms revealed rotation of the negative/positive (N1/P2) polarity sunspots in the opposite directions, which increased the right and left-handed twist in the magnetic structures rooted at N1/P2. Rapid photospheric flux cancellation (duration$\sim$20-30 min, rate$\approx$3.44$\times$10${}^{20}$ Mx h${}^{-1}$) was observed during and even after the first B6.0 flare and continued until the end of the second C2.3 flare. The RHESSI X-ray sources were located at the site of the loop's coalescence. To the best of our knowledge, such a clear interaction of chromospheric loops along with rapid flux cancellation has not been reported before. These high-resolution observations suggest the formation of a small flux rope by a series of magnetic reconnection within chromospheric loops associated with very rapid flux cancellation.

arXiv commentA&A, in press, 12 pages, 12 figures

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• Decoding the Pre-Eruptive Magnetic Field Configurations of Coronal Mass Ejections
• Origin and Structures of Solar Eruptions I: Magnetic Flux Rope (Invited Review)
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• Multiwavelength Study of Equatorial Coronal-Hole Jets
• The eruption of a small-scale emerging flux rope as the driver of an M-class flare and a coronal mass ejection
• When do solar erupting hot magnetic flux ropes form?
• Filament Eruption and Its Reformation Caused by Emerging Magnetic Flux
• Observation of a Large-scale Quasi-circular Secondary Ribbon associated with Successive Flares and a Halo CME
• Predictions of DKIST/DL-NIRSP observations for an off-limb kink-unstable coronal loop
• The dynamics of AR 12700 in its early emerging phase I: interchange reconnection
• The dynamics of AR 12700 in its early emerging phase II: fan-shaped activities relevant to arch filament systems