Solar Flare Prediction Using Magnetic Field Diagnostics above the Photosphere

In this article, we present the application of the weighted horizontal gradient of magnetic field (WG_M) flare prediction method to three-dimensional (3D) extrapolated magnetic configurations of 13 flaring solar active regions (ARs). The main aim is to identify an optimal height range, if any, in the interface region between the photosphere and lower corona, where the flare onset time prediction capability of WG_M is best exploited. The optimal height is where flare prediction, by means of the WG_M method, is achieved earlier than at the photospheric level. 3D magnetic structures, based on potential and nonlinear force-free field extrapolations, are constructed to study a vertical range from the photosphere up to the low corona with a 45 km step size. The WG_M method is applied as a function of height to all 13 flaring AR cases that are subject to certain selection criteria. We found that applying the WG_M method between 1000 and 1800 km above the solar surface would improve the prediction of the flare onset time by around 2-8 hr. Certain caveats and an outlook for future work along these lines are also discussed.