Sign singularity and flares in solar active region NOAA 11158

Solar Active Region NOAA 11158 has hosted a number of strong flares, including one X2.2 event. The complexityof current density and current helicity are studied through cancellation analysis of their sign-singular measure,which features power-law scaling. Spectral analysis is also performed, revealing the presence of two separatescaling ranges with different spectral index. The time evolution of parameters is discussed. Sudden changes of thecancellation exponents at the time of large flaresand the presence of correlation with Extreme-Ultra-Violet and X-ray flux suggest that eruption of large flares can be linked to the small-scale properties of the current structures.