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Session 22 - Radio - Loud AGN & Extragalactic Jets.
Display session, Wednesday, January 07
Exhibit Hall,

[22.07] Self-Organized Criticality in Accretion Disks?

Y. Xiong, G. Bao, P. J. Wiita (Georgia St.U.)

We present the results of computer simulations of self-organized criticality models as applied to the variability of X-ray emission from accretion disks. Light-curves and resulting variability power spectra are computed for variations in parameters such as: the ratios of the inner to outer radii of the unstable portion of the accretion disk; amount of differential rotation; and initial deviation from criticality. Comparisons are made between models computed with and without relativistic effects, and changes in the power spectrum index with the inclination at which the disk is viewed also are demonstrated. The physical relevance of this class of model for active galactic nuclei X-ray variability data is considered. We conclude that self-organized criticality in the exact sense is not produced, although the range of power spectra indices is very similar to those observed. This is because the power spectrum index is a fairly strong function of the boundary locations if the energy release is dependent upon radial location, as is likely to be the case for plausible models associated with disks.

This work was supported in part by NASA grant NAG 5-3098.

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