Supersonic downflows in the vicinity of a growing pore evidence of unresolved magnetic fine structure at chromospheric heights

Aims. The velocity and magnetic fine structure of the chromosphere at the leg of an emerging magnetic loop is investigated at a location of supersonic downflows. Methods. We analyze a time series of spectropolarimetric data in the He I 1083 nm triplet covering a time interval of ≈70 min. The temporal evolution as well as the topology of the magnetic field in the downflow region are investigated. We apply an inversion technique based on a genetic algorithm using the Milne-Eddington approach. The technique is very reliable and robust in retrieving maps of the velocity and the magnetic field vector for both atmospheric components separately. Results. We observe redshifts corresponding to a downflow speed of up to 40 km s^-1 in the vicinity of a growing pore. These super-sonic downflows always coexist with a second atmospheric component almost at rest (slow component) within the same resolution element. The redshifted component is more inclined to the solar normal than the slow component and has a different field strength. Conclusions. We interpret this downflow as a consequence of the draining of the rising loops. The different magnetic field orientation of the redshifted and the slow component give rise to two possible interpretations: an uncombed structure of the chromosphere, similar to the differently inclined flux-tubes in the penumbra of a sunspot, or a cloud-like structure containing gas at different velocities in two separate height layers of the solar atmosphere.