Authors: Vasyl Yurchyshyn (Big Bear Solar Observatory), Seth Garland (Sagamore Hill Solar Observatory)

We present an investigation of the 3D coronal magnetic field evolution associated with 30 major solar flares (18 X-class and 12 M-class) to identify consistent pre-eruptive signatures and their relationship to flare properties. Utilizing 12-minute cadence SDO/HMI photospheric vector magnetograms, we performed Non-Linear Force-Free Field (NLFFF) extrapolations spanning two hours centered on each flare’s onset. We calculated various magnetic parameters – including total unsigned flux, F, free magnetic energy (E_free), and total unsigned magnetic twist (Tw) – across localized non-potential regions (NPRs).

Superposed epoch analysis and Spearman ranking correlations reveal that E_free and T show the most discernible pre-eruptive trends, displaying strong to very strong correlations (r_s = 0.6–0.85) with peak X-ray flux, duration, and integrated flux. Detailed case studies of NOAA Active Regions 11944 and 11429 further demonstrate that high-twist regions (Tw > 1.5) and areas of high magnetic field strength (|B| > 1000 G) spatially coincide with initial flare brightenings, providing a tool for predicting flare localization. Furthermore, we find that the kinematic evolution of eruptions, such as the slow rise of the X1.2 flare and subsequent CME deflection, is driven by the decay index and slanted magnetic boundaries of the surrounding sunspot fields. Sign-singularity analysis confirms rapid, coordinated variations in current systems and helicity prior to event onset, followed by their exhaustion. Collectively, these results suggest that 3D magnetic parameters and MFR diagnostics can effectively characterize the stability, timing, and spatial configuration of eruptive solar phenomena.