Active region helicity properties from magnetic tongues

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

Moscú

Congreso; The 40th COSPAR Scientific Assembly; 2014

Committee on Space Research

p { margin-bottom: 0.21cm; }We study the evolution of photosphericmagnetic tongues to infer the magnetic helicity sign of a large setof active regions (ARs) observed during Solar Cycle 23. Magnetictongues appear during the emergence of twisted toroidal magnetic fluxtubes that form ARs due to contribution of the azimuthal component ofthe magnetic field around the torus axis. The method to compute thehelicity sign is based on the determination of the polarity inversionline (PIL) and its relative orientation respect to the direction ofthe AR main bipolar axis (the AR´s tilt), as well as the analysis ofits evolution during the AR emergence. We analyze a set of 150bipolar ARs observed with SOHO/MDI between 1996 and 2010. The PILmethod, as tested in previous works, needs ARs with simple bipolarstructures and devoid of backgroud magnetic remnants in order toprovide reliable computations. Therefore, the low number of sunspotsregistered along the mínimum between Cycles 23 and 24 is afavourable period to find simple isolated ARs. We determine a seriesof statistical properties of the studied ARs, such as the latitudinaland hemispherical dependence of the magnetic helicity sign, the ARtilt, the total unsigned magnetic flux, and the presence ofasymmetries between the main polarities.