  Active galactic nuclei (AGN) light curves observed with different wavebands
show that the variability in longer wavelength bands lags the variability in
shorter wavelength bands. Measuring these lags, or reverberation mapping, is
used to measure the radial temperature profile and extent of AGN disks,
typically with a reprocessing model that assumes X-rays are the main driver of
the variability in other wavelength bands. To demonstrate how this reprocessing
works with realistic accretion disk structures, we use 3D local shearing box
multi-frequency radiation magnetohydrodynamic (MHD) simulations to model the
UV-emitting region of an AGN disk, which is unstable to the magnetorotational
instability (MRI) and convection. At the same time, we inject hard X-rays
($>1$~keV) into the simulation box to study the effects of X-ray irradiation on
the local properties of the turbulence and the resulting variability of the
emitted UV light curve. We find that disk turbulence is sufficient to drive
intrinsic variability in emitted UV light curves and that a damped random walk
(DRW) model is a good fit to this UV light curve for timescales $>5$~days.
Meanwhile, the injected X-rays have almost no impact on the power spectrum of
the emitted UV light curve. In addition, the injected X-ray and emitted UV
light curves are only correlated if there is X-ray variability on timescales
$>1$~day, in which case we find a correlation coefficient $r=0.52$. These
results suggest that hard X-rays with scattering dominated opacity are likely
not the main driver of the reverberation signals.
