Fields and Flares: Understanding the Complex Magnetic Topologies of Solar Active Regions

TL;DR

This study investigates the magnetic field evolution in sunspots and their connection to solar flares, revealing rapid pre-flare magnetic changes and coronal energy dynamics using high-resolution data and 3D extrapolation.

Contribution

It provides new insights into the rapid magnetic field changes before flares and demonstrates the use of 3D magnetic extrapolation to study coronal magnetic energy evolution.

Findings

Significant increases in vertical magnetic field strength and current density before flares.

First observations of spatial changes in magnetic field inclination across neutral lines.

Coronal magnetic energy increases hours before flares and decreases afterward.

Abstract

Sunspots are regions of decreased brightness on the visible surface of the Sun (photosphere) that are associated with strong magnetic fields. They have been found to be locations associated with solar flares, which occur when energy stored in sunspot magnetic fields is suddenly released. The processes involved in flaring and the link between sunspot magnetic fields and flares is still not fully understood, and this thesis aims to gain a better understanding of these topics. The magnetic field evolution of a number of sunspot regions is examined using high spatial resolution data from the Hinode spacecraft. The research presented in this thesis gives insight into both photospheric and coronal magnetic field evolution of flaring regions. Significant increases in vertical field strength, current density, and field inclination angle towards the vertical are observed in the photosphere just hours before a flare occurs, which is on much shorter timescales than previously studied. First observations of spatial changes in field inclination across a magnetic neutral line (generally believed to be a typical source region of flares) are also discovered. 3D magnetic field extrapolation methods are used to study the coronal magnetic field, using the photospheric magnetic field data as a boundary condition. Magnetic energy and free magnetic energy are observed to increase significantly a few hours before a flare, and decrease afterwards, which is a similar trend to the photospheric field parameter changes observed. Evidence of partial Taylor relaxation is also detected after a flare, as predicted by several previous studies. The results outlined in this thesis show that this particular field of research is vital in furthering our understanding of the magnetic nature of sunspots and its link to flare processes.