Signed measures of stochastic fields show a sign-singular behavior related to extreme and violent oscillations in sign. On the basis of vector magnetic field measurements in active regions, we calculate the current helicity in the photosphere and we show that, for all 22 active regions we examined, the signed measure is sign-singular. Our results allow us to address the problem of (dc) magnetic field energy build up in the solar atmosphere. In fact, it has been shown that the necessary condition for the alpha-effect is the presence of a predominant sign of current helicity over a given volume. Sign-singularity represents a signature of a scaling phenomenon underlying the dominance of a sign of the current helicity at a certain scale, thus experimentally confirming the presence of necessary condition for alpha-effect. With our method, we are able to address also the scaling laws of turbulence in the transverse magnetic field of the photosphere. Our method represents a new way of investigating vector magnetograms in the photosphere by looking at new statistical concepts. In this sense it can be applied to active regions where the determination of quantities through the visual inspection of H alpha patterns is not reliable.
IAU Joint Discussion
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