  Context. Active regions (ARs) appear in the solar atmosphere as a consequence
of the emergence of magnetic flux tubes. The presence of elongated magnetic
polarities in line-of-sight (LOS) magnetograms indicates the existence of twist
in the flux tubes forming them. These polarity elongations, called magnetic
tongues, bias the measurement of AR characteristics obtained during their
emergence phase (e.g. their tilt angle and magnetic flux, among others). In
particular, obtaining a good estimation of the tilt angle evolution plays a key
role in constraining flux-transport dynamo models. Aims. In this work we aim to
estimate the intrinsic properties of the twisted flux tubes, or flux ropes,
that form ARs by quantitatively comparing observed LOS magnetograms with
synthetic ones derived from a toroidal magnetic flux tube model. Methods. For
this reason, we develop a Bayesian inference method to obtain the statistical
distributions of the inferred model parameters. As an example, we apply the
method to NOAA AR 10268. Next, we test the results using a synthetic-AR
generator to quantify the effect of small scale perturbations over the inferred
parameter distributions. Results. We conclude that this method can
significantly remove the effects of magnetic tongues on the derived AR global
characteristics, providing a better knowledge of the intrinsic properties of
the emerging flux rope. Conclusions. These results provide a framework for
future analysis of the physical properties of emerging ARs using Bayesian
statistics.
