Speaker
Description
In recent decades, diverse catastrophic phenomena, from earthquakes and landslides to structural collapses and myocardial infarctions, have been framed as critical transitions in complex systems, marked by a sudden, irreversible shift from equilibrium to an unstable state. Here, we extend for the first time the Natural Time Analysis (NTA) framework to solar Active Regions (ARs) in order to identify reliable precursors of flare initiation. Using time series of magnetograms from Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory and the corresponding SHARP indices (total magnetic flux, magnetic shear angle, current helicity, etc.), we construct event sequences weighted by energy to probe the AR dynamic evolution. Case studies of M-flare-productive ARs reveal pronounced changes in the NTA parameters, most notably in current helicity, immediately before flare onset, whereas a control set of non-flaring regions shows no analogous critical signatures. These results validate NTA as a powerful tool for solar flare nowcasting and suggest that current helicity may serve as a key indicator of the approach to criticality. This novel application not only enriches our understanding of the physical mechanisms underlying flare triggering within the theory of critical phenomena but also offers a promising operational technique for short-term space-weather forecasting.
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