Calculating energy storage due to topological changes in emerging active region NOAA AR 11112

TL;DR

This paper introduces an automated method to track magnetic flux changes and compute energy storage in the solar corona, applied to NOAA AR 11112, revealing significant energy buildup before a flare.

Contribution

The authors developed an algorithm to estimate flux emergence/submergence and maintain a consistent connectivity matrix over time for energy calculations.

Findings

Estimated magnetic energy buildup of ~8.25 x 10^30 ergs over 3 days.

Applied the method to NOAA AR 11112 before a major flare.

Demonstrated the importance of accounting for flux emergence/submergence.

Abstract

The Minimum Current Corona (MCC) model provides a way to estimate stored coronal energy using the number of field lines connecting regions of positive and negative photospheric flux. This information is quantified by the net flux connecting pairs of opposing regions in a connectivity matrix. Changes in the coronal magnetic field, due to processes such as magnetic reconnection, manifest themselves as changes in the connectivity matrix. However, the connectivity matrix will also change when flux sources emerge or submerge through the photosphere, as often happens in active regions. We have developed an algorithm to estimate the changes in flux due to emergence and submergence of magnetic flux sources. These estimated changes must be accounted for in order to quantify storage and release of magnetic energy in the corona. To perform this calculation over extended periods of time, we must additionally have a consistently labeled connectivity matrix over the entire observational time span. We have therefore developed an automated tracking algorithm to generate a consistent connectivity matrix as the photospheric source regions evolve over time. We have applied this method to NOAA Active Region 11112, which underwent a GOES M2.9 class flare around 19:00 on Oct.16th, 2010, and calculated a lower bound on the free magnetic energy buildup of ~8.25 x 10^30 ergs over 3 days.