Applying the weighted horizontal magnetic gradient method to a simulated flaring Active Region

TL;DR

This study tests the weighted horizontal magnetic gradient ($WG_M$) as a flare precursor using MHD simulations of solar-like flares, finding it effective at predicting flare timing and location at specific heights.

Contribution

It demonstrates the applicability of the $WG_M$ method as a reliable flare precursor in simulated active regions, identifying optimal heights for prediction.

Findings

$WG_M$ precursors are identifiable at specific heights before flares.

Estimated flare onset times match actual flare times in simulations.

Optimal heights for flare prediction align with thermal and Ohmic heating signatures.

Abstract

Here, we test the weighted horizontal magnetic gradient ($WG_M$) as a flare precursor, introduced by Korsos et. al. (2015, ApJ, 802, L21), by applying it to a magneto-hydrodynamic (MHD) simulation of solar-like flares Chatterjee et. al. (2016, Physical Review Letters, 116, 10, 101101). The pre-flare evolution of the $WG_M$ and the behavior of the distance parameter between the area-weighted barycenters of opposite polarity sunspots at various heights is investigated in the simulated $\delta$-type sunspot. Four flares emanated from this sunspot. We found the optimum heights above the photosphere where the flare precursors of the $WG_M$ method are identifiable prior to each flare. These optimum heights agree reasonably well with the heights of the occurrence of flares identified from the analysis of their thermal and Ohmic heating signatures in the simulation. We also estimated the expected time of the flare onsets from the duration of the approaching-receding motion of the barycenters of opposite polarities before each single flare. The estimated onset time and the actual time of occurrence of each flare are in good agreement at the corresponding optimum heights. This numerical experiment further supports the use of flare precursors based on the $WG_M$ method.