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We present a detailed temporal analysis of a set of hydrodynamic andmagnetohydrodynamic (MHD) simulations of geometrically-thin (h/r~0.05) blackhole accretion disks. The black hole potential is approximated by thePaczynski-Wiita pseudo-Newtonian potential. In particular, we use oursimulations to critically assess two widely discussed models for high-frequencyquasi-periodic oscillations, global oscillation modes (diskoseismology) andparametric resonance instabilities. We find that initially disturbedhydrodynamic disks clearly display the trapped global g-mode oscillationpredicted by linear perturbation theory. In contrast, the sustained turbulenceproduced in the simulated MHD disks by the magneto-rotational instability doesnot excite these trapped g-modes. We cannot say at present whether the MHDturbulence actively damps the hydrodynamic g-mode. Our simulated MHD disks alsofail to display any indications of a parametric resonance instability betweenthe vertical and radial epicyclic frequencies. On the other hand, we do seecharacteristic frequencies at any given radius in the disk corresponding tolocal acoustic waves. We also conduct a blind search for any quasi-periodicoscillation in a proxy lightcurve based on the instantaneous mass accretionrate of the black hole, and place an upper limit of 2% on the total power inany such feature. We highlight the importance of correcting for secular changesin the simulated accretion disk when performing temporal analyses.

On the time variability of geometrically-thin black hole accretion disks I : the search for modes in simulated disks