Simultaneous Visible and Infrared Spectro-polarimetry of a Solar Internetwork Region

We present the first simultaneous infrared (IR) and visible spectro-polarimetric observations of a solar internetwork region. The Fe I lines at λ6301.5 Å, λ6302.5 Å, λ15648 Å, and λ15652 Å were observed, with a lag of only 1 min, using highly sensitive spectro-polarimeters operated in two different telescopes (VTT and THEMIS at the Observatorio del Teide). Some 30% of the observed region shows IR and visible Stokes V signals above noise. These polarization signals indicate the presence of kG magnetic field strengths (traced by the visible lines) co-existing with sub-kG fields (traced by the infrared lines). In addition, one quarter of the pixels with signal have visible and IR Stokes V profiles with opposite polarity. We estimate the probability density function of finding each longitudinal magnetic field strength in the region. It has a tail of kG field strengths that accounts for most of the (unsigned) magnetic flux of the region. Subject headings: Sun: magnetic fields – Sun: photosphere