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We analyse the temporal evolution of the Differential Emission Measure (DEM)of solar active regions and explore its usage in solar flare prediction. TheDEM maps are provided by the Gaussian Atmospheric Imaging Assembly (GAIA-DEM)archive, calculated assuming a Gaussian dependence of the DEM on thelogarithmic temperature. We analyse time-series of sixteen solar active regionsand a statistically significant sample of 9454 point-in-time observationscorresponding to hundreds of regions observed during solar cycle 24. Thetime-series analysis shows that the temporal derivatives of the EmissionMeasure dEM/dt and the maximum DEM temperature dTmax/dt frequently exhibit highpositive values a few hours before M- and X-class flares, indicating thatflaring regions become brighter and hotter as the flare onset approaches. Fromthe point-in-time observations we compute the conditional probabilities offlare occurrences using the distributions of positive values of the dEM/dt, anddTmax/dt and compare them with corresponding flaring probabilities of the totalunsigned magnetic flux, a conventionally used, standard flare predictor. ForC-class flares, conditional probabilities have lower or similar values with theones derived for the unsigned magnetic flux, for 24 and 12 hours forecastwindows. For M- and X-class flares, these probabilities are higher than thoseof the unsigned flux for higher parameter values. Shorter forecast windowsimprove the conditional probabilities of dEM/dt, and dTmax/dt in comparison tothose of the unsigned magnetic flux. We conclude that flare forerunner eventssuch as preflare heating or small flare activity prior to major flares reflecton the temporal evolution of EM and Tmax. Of these two, the temporal derivativeof the EM could conceivably be used as a credible precursor, or short-termpredictor, of an imminent flare.

Differential Emission Measure Evolution as a Precursor of Solar Flares