  We point out that luminous magnetic flares, thought to occur in standard AGN
accretion disks, cannot be located much higher than few pressure scale heights
above the disk. Using this fact, we estimate the fraction of the disk surface
illuminated by a typical flare. This fraction turns out to be very small for
geometrically thin disks, which implies that the instantaneous Fe K-alpha
emission line from a specific magnetic flare is narrow. The line is red- or
blue-shifted depending on the position of the observer relative to the flare
and sweeps across the line band with time. We present several examples of
theoretical time-resolved line profiles from such flares for a non-rotating
black hole. The observations of such moving features with future X-ray
telescopes will present a powerful test of the accretion disk geometry and may
also test General Relativity in the strong field limit.
