The causality between the rapid rotation of a sunspot and an X3.4 flare

TL;DR

This study investigates how rapid sunspot rotation influences magnetic field twisting and leads to an X3.4 flare, providing evidence of causality between sunspot dynamics and solar flare activity.

Contribution

It demonstrates the causal link between sunspot rotation, magnetic field shearing, and flare triggering using multi-wavelength observations and magnetogram analysis.

Findings

Sunspot exhibited counterclockwise rotation before the flare.

Magnetic field lines became highly sheared along the neutral line.

Formation of sheared loops and inverse S-shaped loops in the corona.

Abstract

Using multi-wavelength data of Hinode, a rapid rotation of a sunspot in active region NOAA 10930 is studied in detail. We found the extra-ordinary counterclockwise rotation of the sunspot with positive polarity before an X3.4 flare. From a series of vector magnetograms, it is found that the magnetic force lines highly sheared along the neutral line accompanying the sunspot rotation. Furthermore, it is also found that the sheared loops and an inverse S-shaped magnetic loop in the corona formed gradually after the sunspot rotation. The X3.4 flare can be reasonably regarded as a result of this movement. The detailed analysis provides an evidence that sunspot rotation leads to magnetic field lines twisting in the photosphere, the twist is then transported into the corona, and finally flares are triggered.