  X-ray spectra from stellar coronae are reprocessed by the underlying
photosphere through scattering and photoionization events. While reprocessed
X-ray spectra reaching a distant observer are at a flux level of only a few
percent of that of the corona itself, characteristic lines formed by inner
shell photoionization of some abundant elements can be significantly stronger.
The emergent photospheric spectra are sensitive to the distance and location of
the fluorescing radiation and can provide diagnostics of coronal geometry and
abundance. Here we present Monte Carlo simulations of the photospheric Kalpha
doublet arising from quasi-neutral Fe irradiated by a coronal X-ray source.
Fluorescent line strengths have been computed as a function of the height of
the radiation source, the temperature of the ionising X-ray spectrum, and the
viewing angle. We also illustrate how the fluorescence efficiencies scale with
the photospheric metallicity and the Fe abundance. Based on the results we make
three comments: (1) fluorescent Fe lines seen from pre-main sequence stars
mostly suggest flared disk geometries and/or super-solar disk Fe abundances;
(2) the extreme ~1400 mA line observed from a flare on V1486 Ori can be
explained entirely by X-ray fluorescence if the flare itself were partially
eclipsed by the limb of the star; and (3) the fluorescent Fe line detected by
Swift during a large flare on II Peg is consistent with X-ray excitation and
does not require a collisional ionisation contribution. There is no convincing
evidence supporting the energetically challenging explanation of electron
impact excitation for observed stellar Fe Kalpha lines.
