The Fundamental Instability of Solar Magnetic Eruptions

We present a simple metric that can adequately quantify the eruptive potential of solar active regions while in their pre-eruption phases. Regions with intense magnetic polarity inversion lines exhibit larger values of this metric, dubbed the effective connected magnetic field strength, Beff. Calculating the pre-flare values of Beff in 93 flaring active regions and the peak Beff-values in 205 non-flaring ones we find a clear segregation between the two populations that helps draw a quantitative distinction between eruptive and non-eruptive active regions. Larger Beff-values statistically correlate with stronger flares and faster, more impulsively accelerated, coronal mass ejections (CMEs). Besides the obvious implications for space weather forecasting, this study underlines the fundamental insight that the Beff metric can bring toward a physical understanding of solar eruptions. A possible new eruption concept may eventually unify previous eruption models, relax excessive requirements posed by some of these models, and naturally explain confined vs. eruptive flares or fast (active-region) vs. slow (quiet-Sun) CMEs.