Joy´s Law determination for emerging active regions

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

Conferencia; XI Conferencia Latinoamericana de Geofísica Espacial (XI COLAGE); 2018

We study the process of emergence of solar active regions (ARs) todetermine the relation between the latitude of emergence and the tilt angleformed with respect to the E-W direction. The relation between the tilt and thelatitude, established by Joy´s law, is a fundamental element for dynamo modelsto explain the mechanisms involved during the inversion of the poloidalmagnetic field. Recent studies based on the observations of the line-of-sight(LOS) magnetic field and the automatic detection of bipoles show a strongdispersion on the obtained law (Stenflo & Kosovichev 2012; Wang et al.2015). We consider that the dispersion can be due to the stage of evolution ofthe analyzed ARs. The LOS projection of the twisted magnetic field of the emergingstructures that form ARs produces an elongation of the magnetic polaritiesknown as magnetic tongues. As we have shown in Poisson et al. (2016, SolarPhys., 291, 1625-1646), magnetic tongues affect the photospheric fielddistribution observed in LOS magnetograms and, consequently, impact on thedetermination of the tilt angle. In this work we analyze the evolution of thetilt angle during the emergence of 186 bipolar ARs using LOS magnetograms. Wetest a novel method to correct the effect of the magnetic tongues on thedetermination of the tilt angle. Furthermore, we estimate the latitudinaldependence of the corrected tilt angle considering different ARs propertiessuch as the magnetic helicity sign, the hemisphere of emergence, and the senseof rotation of the bipole. Finally, we quantify the effect of the twist on thedispersion found when determining the Joy´s law.