Modeling the photospheric magnetic field distribution of emerging solar active regions

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

Reunión virtual

Conferencia; Applications of Statistical Methods and Machine Learning in the Space Sciences; 2021

Active regions (ARs) appear in the solar atmosphere as a consequence of the emergence of magneticux tubes. It has been shown that in order to survive their transit through the convective zone,these ux tubes should be twisted, forming so-called magnetic ux-ropes (FR) and transporting withthem magnetic helicity from the solar interior. This quantity plays a key role in the production ofenergetic events such as ares and coronal mass ejections. Photospheric observations of the line-of-sight (LOS) component of the magnetic eld reveal that during the emergence of ARs the presenceof twisted eld lines around the FR axis produces an elongation of the main AR magnetic polaritiesknown as magnetic tongues. In this work we aim to estimate the intrinsic geometrical propertiesof FRs, by comparing LOS magnetograms of emerging ARs with synthetic magnetograms derivedfrom a toroidal magnetic ux tube model. In particular, we estimate the tilt angle, dened as theinclination of the AR main bipolar axis with respect to the solar equator, which is strongly affectedby magnetic tongues. Our method uses a probabilistic scheme based on the Bayes theorem to inferthe most probable intrinsic parameters of an emerging ux tube, assuming a normal departure be-tween the model and the observations. Open access python 3 packages, pymc3 and Theano are usedto optimize the sampling of the model 8-dimensional parameterco space. Analyzing a sequence of66 magnetograms, we are able to infer the most probable values of the intrinsic parameters for AR10268, including its magnetic helicity content and its intrinsic tilt angle.