Magnetic helicity properties of emerging active regions determined from longitudinal photospheric magnetograms

POISSON, M.; LÓPEZ FUENTES, M.C.; MANDRINI, C.H.; DÉMOULIN, P.

Mysore

Congreso; 39th COSPAR General Assembly; 2012

COSPAR

We study the emergence of solar active regions (ARs) to determine how their magnetic helicity properties a ect the evolution of the photospheric ux observed in SOHO/MDI magnetograms. We characterize the so called magnetic tongues (Luoni et al. 2011, Solar Phys. 270, 45), which are produced by the line of sight projection of the azimuthal component of the magnetic eld in twisted emerging ux-tubes that form ARs. We analyze a set of approximately 40 ARs observed between 2004 and 2007. We only select ARs for which the full emergence process is observable on the solar disk. In order to minimize the background eld contribution we select cases that emerge in areas devoid of remnant ux from older ARs. From the selected ARs magnetograms we determine and study the evolution of a series of parameters, such as the tilt angle, the polarity inversion line orientation, the magnetic ux of ARs, as well the size and the shape of the polarities and their tongues. We also analyze preceding-following polarities assymetries. We compare our results with other magnetic helicity determinations and conclude on how to use the analyzed parameters as alternative helicity proxies. Since ARs with high contents of magnetic helicity are in general the most productive in term of ares and CMEs, the possible determination of the magnetic helicity properties of ARs from the very beginning of their emergence can be a powerful forecast tool for solar activity.