Generation mechanisms of quasi-parallel and quasi-circular flare ribbons in a confined flare

Abstract

We analyze a confined multiple-ribbon M2.1 flare (SOL2015-01-29T11:42) that originated from a fan-spine coronal magnetic field configuration, within active region NOAA 12268. The observed ribbons form in two steps. First, two primary ribbons form at the main flare site, followed by the formation of secondary ribbons at remote locations. We observe a number of plasma flows at extreme-ultraviolet temperatures during the early phase of the flare (as early as 15 min before the onset) propagating towards the formation site of the secondary ribbons. The secondary ribbon formation is co-temporal with the arrival of the pre-flare generated plasma flows. The primary ribbons are co-spatial with RHESSI hard X-ray sources, whereas no enhanced X-ray emission is detected at the secondary ribbons sites. The (E)UV emission, associated with the secondary ribbons, peaks ~1 min after the last RHESSI hard X-ray enhancement. A nonlinear force-free model of the coronal magnetic field reveals that the secondary flare ribbons are not directly connected to the primary ribbons, but to regions nearby. Detailed analysis suggests that the secondary brightenings are produced due to dissipation of kinetic energy of the plasma flows (heating due to compression), and not due to non-thermal particles accelerated by magnetic reconnection, as is the case for the primary ribbons.

18 pages, 11 figures, accepted for publication in ApJ

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Cited by in corpus (11)

• Transition from circular-ribbon to parallel-ribbon flares associated with a bifurcated magnetic flux rope
• Imaging and spectral study on the null point of a fan-spine structure during a solar flare
• Development of a Confined Circular-cum-parallel Ribbon Flare and Associated Pre-flare Activity
• Evolutionary stages and triggering process of a complex eruptive flare with circular and parallel ribbons
• Detections of Multi-Periodic Oscillations during a Circular Ribbon Flare
• Pre-eruption processes: heating, particle acceleration and the formation of a hot channel before the 2012 October 20 M9.0 limb flare
• Statistical analysis of circular-ribbon flares
• Successive occurrences of quasi-circular ribbon flares in a fan-spine-like configuration involving hyperbolic flux tube
• Fast degradation of the circular flare ribbon on 2014 August 24
• Energy Partition in Four Confined Circular-Ribbon Flares
• A Hot Cusp-Shaped Confined Solar Flare