Constraining 3D Magnetic Field Extrapolations Using The Twin Perspectives of STEREO

TL;DR

This paper uses twin perspectives from STEREO to constrain 3D magnetic field extrapolations of a solar active region, improving understanding of magnetic topology, twist, and energy changes during flux emergence.

Contribution

It introduces a method combining EUV imaging with magnetic extrapolation constraints from STEREO data to accurately determine magnetic field twist and topology.

Findings

Flux emergence causes significant changes in magnetic topology.

Magnetic energy of the region varies with flux emergence.

Extrapolation constrained by STEREO improves magnetic field modeling.

Abstract

The 3D magnetic topology of a solar active region (NOAA 10956) was reconstructed using a linear force-free field extrapolation constrained using the twin perspectives of \emph{STEREO}. A set of coronal field configurations was initially generated from extrapolations of the photospheric magnetic field observed by the Michelson Doppler Imager (MDI) on \emph{SOHO}. Using an EUV intensity-based cost function, the extrapolated field lines that were most consistent with 171\AA\ passband images from the Extreme UltraViolet Imager (EUVI) on \emph{STEREO} were identified. This facilitated quantitative constraints to be placed on the twist ($\alpha$) of the extrapolated field lines, where $\nabla \times {\bf B} = \alpha {\bf B}$. Using the constrained values of $\alpha$, the evolution in time of twist, connectivity, and magnetic energy were then studied. A flux emergence event was found to result in significant changes in the magnetic topology and total magnetic energy of the region.