Forecasting coronal mass ejections from line-of-sight magnetograms

We show that the length of strong-gradient, strong-field main neutral line, LSGM, which can be measured from line-of-sight magnetograms such as from SOHO/MDI, is both a measure of active-region nonpotentiality and a useful predictor of an active region's future Coronal mass ejections (CME) productivity. To demonstrate that LSGM is a nonpotentiality measure, we show that it is strongly correlated with a direct measure of nonpotentiality. For an appropriate choice of a threshold value, an active region's measured LSGM can be used as a predictor of whether the active region will produce a CME within a few days after the magnetogram. For our set of 36 Marshall Space Flight CentreMSFC vector magnetograms of bipolar active regions, LSGM is found to have a success rate of 80% for prediction of CME productivity in the 0-2 day window. The development of LSGM as a method of measuring nonpotentiality for forecasting large, fast CMEs from present space-based assets is of value to NASA's space exploration initiative (manned missions to the Moon and Mars).