Three-lobed near-infrared Stokes V profiles in the quiet Sun

Abstract

Context. The 1.5-m GREGOR solar telescope can resolve structures as small as 0.4′′ at near-infrared wavelengths on the Sun. At this spatial resolution the polarized solar spectrum shows complex patterns, such as large horizontal and/or vertical variations of the physical parameters in the solar photosphere. Aims. We investigate a region of the quiet solar photosphere exhibiting three-lobed Stokes V profiles in the Fe I spectral line at 15 648 Å. The data were acquired with the GRIS spectropolarimeter attached to the GREGOR telescope. We aim at investigating the thermal, kinematic and magnetic properties of the atmosphere responsible for these measured complex signals. Methods. The SIR inversion code is employed to retrieve the physical parameters of the lower solar photosphere from the observed polarization signals. We follow two different approaches. On the one hand, we consider that the multi-lobe circular polarization signals are only produced by the line-of-sight variation of the physical parameters. We therefore invert the data assuming a single atmospheric component that occupies the entire resolution element in the horizontal plane and where the physical parameters vary with optical depth τ (i.e., line-of-sight). On the other hand, we consider that the multi-lobe circular polarization signals are produced not by the optical depth variations of the physical parameters but instead by their horizontal variations. Here we invert the data assuming that the resolution element is occupied by two different atmospheric components where the kinematic and magnetic properties are constant along the line-of-sight. Results. Both approaches reveal some common features about the topology responsible for the observed three-lobed Stokes V signals: both a strong (>1000 Gauss) and a very weak (<10 Gauss) magnetic field with opposite polarities and harboring flows directed in opposite directions must co-exist (either vertically or horizontally interlaced) within the resolution element. Conclusions.