Solar MnI 5432/5395 angstrom line formation explained

We present a solution for the long standing problem concerning the "chromos pheric" behaviour of the Mn I 5395/5432 Angstrom lines in the solar spectru m using multi-line/multi-species NLTE modelling. Using comprehensive spectr al line formation modelling, we show that the Mn I lines are very sensitive to optical pumping in a transition which overlaps with Mg II k. It therefo re follows that one has to be careful with the choice of lines as temperatu re indicators and for the determination of the Mn abundances although on th e other hand, due to the formation process of these lines they mag; be usef ul as a solar and stellar activity diagnostic.