Evolution of ARs at photosphere before flare and CME occurrence

We propose the introduction of new measures of pre-flare and pre-CME behaviour of by analysing the evolution of active regions using the Debrecen Sunspot Data catalogue. The proxy measure of our approach is the so-called weighted horizontal gradient of magnetic field (WGM) defined between spots of opposite polarities closer to the neutral line of an AR. The value and the temporal variation of WGM is found to possess novel, very interesting and potentially important diagnostic information about (i) the intensity of expected flares, (ii) the accuracy of onset time prediction, and (iii) whether a flare, with same energetic class in terms of the GOES classification, is followed by another one within 18 hours.
We also suggest the introduction of further two parameters characterising ARs for warning purposes for pre-flare and CME prediction and follow-up monitoring. One is the so-called daily average of the horizontal magnetic gradient (GDS ) and the other is the separation parameter (Sl-f ). These pre-cursor parameters seem to be useful in practice by means of estimating the level of separation of opposite polarities in ARs. By comparing their temporal variation before 24 (or even up to 48) hours prior to flare event one can reliably assess (within errors) the risk of an associated CME.