Intensity and formation height at selected spectral features of the Mg II k line. The top panels show the brightness temperature at k_2v (panel a), k₃ (panel b), and k_2r (panel c) as classified by the peak-finding algorithm. The bottom panels show the height at an optical depth of unity at the wavelength of k_2v (panel d), k₃ (panel e), and k_2r (panel f). Red pixels indicate those where no feature could be detected. The data correspond to the non-degraded muram_en_499000_379s snapshot.