Multiwavelength study of a Solar Eruption from AR NOAA 11112 I. Flux Emergence, Sunspot Rotation and Triggering of a Solar Flare

TL;DR

This study investigates the magnetic flux emergence, sunspot rotation, and magnetic interactions leading to an M2.9 solar flare in NOAA AR 11112, highlighting the role of twisted flux tubes and magnetic reconnection in flare triggering.

Contribution

It provides detailed multiwavelength observations linking flux emergence, sunspot rotation, and magnetic helicity to flare initiation, supporting models of twisted flux tube emergence.

Findings

Flux emergence preceded the flare by 50 hours.

Sunspots exhibited significant rotation and translation.

High-speed plasmoid ejection indicated magnetic reconnection.

Abstract

We analyse the multiwavelength observations of an M2.9/1N flare that occurred in the active region (AR) NOAA 11112 in the vicinity of a huge filament system on 16 October 2010. SDO/HMI magnetograms reveal the emergence of a bipole (within the existing AR) 50 hours prior to the flare event. During the emergence, both the positive and negative sunspots in the bipole show translational as well as rotational motion. The positive polarity sunspot shows the significant motion/rotation in the south-westward/clockwise direction and continuously pushing/sliding the surrounding opposite polarity field region. On the other hand, the negative polarity sunspot moves/rotates in the westward/anticlockwise direction. The positive polarity sunspot rotates ~70 deg. within 30 hours, whereas negative polarity ~20 deg. within 10 hours. SDO/AIA 94 {\AA} EUV images show the emergence of a flux tube in the corona consistent with the emergence of the bipole in HMI. A high speed plasmoid ejection (speed~1197 km/s) was observed during the flare impulsive phase, which suggests the magnetic reconnection of the emerged positive polarity sunspot with the surrounding opposite polarity field region. The entire AR shows the positive helicity injection before the flare event. Moreover, the newly emerging bipole reveal the signature of negative (left-handed) helicity. These observations provide the unique evidences of the emergence of twisted flux tube from below the photosphere to coronal heights triggering a flare mainly due to the interaction between the emerged positive polarity sunspot and a nearby negative polarity sunspot by the shearing motion of the emerging positive sunspot towards the negative one. Our observations also strongly support the idea that the rotation is most likely attributed to the emergence of twisted magnetic fields, as proposed by recent models.