The Evolution of Sunspot Magnetic Fields Associated with a Solar Flare

TL;DR

This study investigates the magnetic field evolution in a solar active region before and after a flare, revealing specific changes in magnetic properties that could aid in flare prediction.

Contribution

It provides detailed observations of magnetic field changes associated with a solar flare, enhancing understanding of flare precursors and post-flare magnetic restructuring.

Findings

Pre-flare increases in vertical magnetic field strength and current density.

Post-flare decrease in vertical field strength and current density.

Inclination angle shifts towards more horizontal after the flare.

Abstract

Solar flares occur due to the sudden release of energy stored in active-region magnetic fields. To date, the pre-cursors to flaring are still not fully understood, although there is evidence that flaring is related to changes in the topology or complexity of an active region's magnetic field. Here, the evolution of the magnetic field in active region NOAA 10953 was examined using Hinode/SOT-SP data, over a period of 12 hours leading up to and after a GOES B1.0 flare. A number of magnetic-field properties and low-order aspects of magnetic-field topology were extracted from two flux regions that exhibited increased Ca II H emission during the flare. Pre-flare increases in vertical field strength, vertical current density, and inclination angle of ~ 8degrees towards the vertical were observed in flux elements surrounding the primary sunspot. The vertical field strength and current density subsequently decreased in the post-flare state, with the inclination becoming more horizontal by ~7degrees. This behaviour of the field vector may provide a physical basis for future flare forecasting efforts.