  Using Chandra HETG data we present light curves for individual spectral lines
of Mg XI and Mg XII for EX Hydrae, an intermediate-polar type cataclysmic
variable. The Mg XI light curve, folded on the white dwarf spin period, shows
two spikes that are not seen in the Mg XII or broad-band light curves.
Occultation of the accretion column by the body of the white dwarf would
produce such spikes for an angle between the rotation axis and the accretion
columns of alpha = 18 degrees and a height of the Mg XI emission above the
white dwarf surface of < 0.0004 white dwarf radii or < 4 km. The absence of
spikes in the Mg XII and broad-band light curves could then be explained if the
bulk of its emission forms at much larger height, > 0.004 white dwarf radii or
> 40 km, above the white dwarf surface, although this is not consistent with
the predictions of the standard Aizu model of the accretion column.
