Multiwavelength Signatures of Episodic Null Point Reconnection in a Quadrupolar Magnetic Configuration and the Cause of Failed Flux Rope Eruption

TL;DR

This study investigates the complex magnetic configurations and multiwavelength signatures associated with a failed solar flare eruption, highlighting the role of null point reconnection and magnetic decay index profiles.

Contribution

It provides detailed observations and analysis of the magnetic field evolution leading to a failed flux rope eruption in a quadrupolar active region.

Findings

Presence of a coronal null point above the core field.

Failed eruption linked to a saddle-like decay index profile.

Multiple small-scale flux enhancements observed before flare.

Abstract

In this paper, we present multiwavelength observations of the triggering of a failed-eruptive M-class flare from the active region NOAA 11302, and investigate the possible reasons for the associated failed eruption. Photospheric observations and Non-Linear Force Free Field extrapolated coronal magnetic field revealed that the flaring region had a complex quadrupolar configuration with a pre-existing coronal null point situated above the core field. Prior to the onset of the M-class flare, we observed multiple periods of small-scale flux enhancements in GOES and RHESSI soft X-ray observations, from the location of the null point. The pre-flare configuration and evolution reported here are similar to the ones presented in the breakout model but at much lower coronal heights. The core of the flaring region was characterized by the presence of two flux ropes in a double-decker configuration. During the impulsive phase of the flare, one of the two flux ropes initially started erupting but resulted in a failed eruption. Calculation of the magnetic decay index revealed a saddle-like profile where decay index initially increased to the torus unstable limits within the heights of the flux ropes but then decreased rapidly reaching to negative values, which was most likely responsible for the failed eruption of the initially torus unstable flux rope.