Three-dimensional Magnetic Reconnection Triggering an X-class Confined Flare in Active Region 12192

Abstract

We present an extensive analysis of the X2.0-class confined flare on 2014 October 27 in the great active region AR 12192, observed by the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory. The slipping motion of the substructures within the negative-polarity flare ribbon (R1) and continual reconnection-induced flows during the confined flare are first presented. The substructures within ribbon R1 were observed to slip in opposite directions at apparent speeds of 10-70 km s −1 . The slipping motion exhibited the quasi-periodic pattern with a period of 80-110 s, which can be observed since the flare start and throughout the impulsive phase of the flare. Simultaneously quasi-periodic flows moved along a reverse-S shaped filament, with an average period of about 90 s. The period of reconnection-induced flows is similar to that of the slippage of ribbon substructures, implying the occurrence of quasi-periodic slipping magnetic reconnection. The spectral observations showed that the Si iv line was blueshifted by 50-240 km s −1 at the location of the flows. During the process of the flare, the filament did not show the rise phase and was not associated with any failed eruption. The flare mainly consisted of two sets of magnetic systems, with both of their east ends anchoring in ribbon R1. We suggest that the slipping magnetic reconnection between two magnetic systems triggers the confined flare.

A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

“…Dudík et al, 2016). IRIS observes substructures moving bi-directionally along the flare ribbons in a couple of events, indicating that reconnection in the quasi-separatrix layer between two flux systems has caused slip-running reconnection to occur (Li et al, 2018b(Li et al, , 2019b. A fan-spine topology was identified in another event using IRIS 2796 Å SJI observations, and because of this topology, slip-running reconnection is identified as a possible trigger mechanism (Zuccarello et al, 2020).…”

“…Janvier, Aulanier, and Démoulin, 2015). On the other hand, puzzling observations of quasi-periodic slipping motions of ribbon substructures for a non-eruptive flare were reported by Li et al (2018b). Despite these observations being reminiscent of the signatures of slipping reconnection, they cannot be simply explained by the standard 3D flare picture, which requires the presence of an eruptive flux rope.…”

Three-dimensional magnetic reconnection in astrophysical plasmas

“…Moreover, both separator and quasi-separator reconnection have been shown to play a role in confined solar flares [161,162]. Li et al [161] found bi-directional slippage of ribbon substructures along a ribbon in a confined flare.…”

“…Moreover, both separator and quasi-separator reconnection have been shown to play a role in confined solar flares [161,162]. Li et al [161] found bi-directional slippage of ribbon substructures along a ribbon in a confined flare. In fact, some confined flares are characterized by slippage and a stable filament, whereas others possess a failed eruption of a filament or flux rope [162].…”

Is flare-ribbon fine structure related to tearing in the flare current sheet?

“…Flare ribbons often have multiple kernels and generally exhibit a complex structure and evolution, especially when viewed in close detail (e.g. Asai et al 2002;Krucker et al 2003;Brannon et al 2015;Jing et al 2016;Li & Zhang 2015;Li et al 2018). For instance, Brannon et al (2015) analysed bright knots and wave-like perturbations in a section of flare ribbon and Parker & Longcope (2017) later tried to explain these findings based on a quasi-two-dimensional tearing analysis involving velocity shear flows.…”