UNNOFIT Inversion of Spectro-Polarimetric Maps Observed with THEMIS

International audienceThis paper presents the inversion of a spectro-polarimetric scan (240 arcsec×340 arcsec) of an active region and a filament, obtained with THEMIS, on December 7, 2003, in the two Fe I lines at 6302.5 Å and 6301.5 Å. The inversion was applied to each line separately, using the UNNOFIT code of tet{b13 La84}, improved by the introduction of a magnetic filling factor parameter. The magnetic and non-magnetic theoretical atmospheres, mixed in the proportion given by the filling factor, are derived from the same set of parameters, except for the presence (or absence) of a magnetic field. The fundamental ambiguity is not solved. The tests run with UNNOFIT show that the magnetic field strength, B, and the magnetic filling factor, α, cannot be separately recovered by the inversion of Fe I 6302.5 Å, but that their product, α B, which is the local average magnetic field, is recovered. The magnetic flux is only its longitudinal component. Our results also reveal two distinct regimes, corresponding to two different ranges of local average magnetic field strength as inferred from Fe I 6302.5 Å: a) The network, having a field inclined of about 20°-30° from the vertical in Fe I 6302.5 Å (more spreaded, but non-horizontal in Fe I 6301.5 Å), with a homogeneous azimuth. In this zone, the local average field strength in Fe I 6302.5 Å is larger than 45 G. b) The internetwork, where the field is turbulent (with a horizontal trend, more spreaded at lower altitudes), and with local average field strength in Fe I 6302.5 Å smaller than 45 G. The two lines gives coherent results, in particular in magnetic field azimuth. From this we conclude that the turbulence of the internetwork field is of solar origin. This work has been presented in detail by tet{b13 Bo06}