Joy's Law determination for emerging active regions

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

Ciudad autónoma de Buenos Aires

Congreso; XI Congreso Latinoamericano de Geofísica Espacial; 2018

Asociación Latianoamericana de Geofísica Espacial

p { margin-bottom: 0.25cm; line-height: 120%; }Westudy the process of emergence of solaractive regions (ARs) to determine the relation between thelatitude of emergence and the tilt angleformed withrespect to the E-W direction. Therelation between the tilt and the latitude, established by Joy´s law,is a fundamental element for dynamo models to explain the mechanismsinvolved during the inversion of the poloidal magnetic field. Recentstudies based on the observationsof the line-of-sight (LOS) magnetic field and the automatic detectionof bipolesshow a strong dispersion on the obtained law (Stenflo &Kosovichev 2012; Wang et al. 2015). We consider that the dispersioncan be due to the stage of evolution of the analyzed ARs. The LOSprojection of the twisted magnetic field of the emerging structuresthat form ARs produces an elongation of the magnetic polarities knownas magnetic tongues. As we have shown inPoisson et al. (2016, Solar Phys., 291, 1625-1646), magnetic tonguesaffect the photospheric fielddistribution observed in LOS magnetograms and, consequently,impact on the determination of the tilt angle. In this work weanalyze the evolution of the tilt angle during the emergence of 186bipolar ARs using LOS magnetograms. We test a novel method to correctthe effect of the magnetic tongues on the determination of the tiltangle. Furthermore, we estimate the latitudinal dependenceof the corrected tilt angle considering different ARs properties suchas the magnetic helicity sign, the hemisphere of emergence, and thesense of rotation of the bipole. Finally, we quantify the effect ofthe twist on the dispersion found whendetermining the Joy´s law.