Demonstration of a weak polarization signal owing to the strong temperature sensitivity of the Fe i line at 5250.2 Å by a comparison of a pixel in a particularly bright BP (red lines) with a pixel located in a much less bright BP (blue lines). a) Vertical temperature stratification as a function of log(τ) at 5000 Å. b) Magnetic field strength stratification. c) and d) Stokes I/I_QS and V/I_QS signals from the original MHD data at the twelve IMaX L12-2 scan positions in the line.