Nuclear reactions in AGN accretion disk

[gleb]

As I understand it, it's all atomic material in the accretion disk of a big black hole, with very high orbital velocities and high density. However, the the disk is quite flat, and cooler than one would think with the velocities involved, because the material is swirling in smoothly, with individual particles having fairly tame velocities relative to nearby particles.

Now, I have two questions, really. First, does my understanding of the very basic properties of accretion disks agree with the currently accepted models? And second, is it possible for fusion to occur in the inner area of the disk? I know that the temperature of the gas is only on the order of x-ray emission, too cool for fusion, but what if there was some sort of perturbation in the disk, something that disrupted it's very smooth inward spiral. To me it seems like with the densities and energies involved, it would be a good environment for nuclear fusion. So, is there any merit to this idea?

 

[Soul Surfer]

It would depend on the size of the black hole and the density of the material in the accretion disc. White dwarfs can have bursts of surface fusion if fed from a companion star so I see no reasons why some black holes will not have fusion explosions in ther accretion discs. They can also disrupt stars by tidal stretching and possibly expose fusion areas.

The bigger the black hole gets the "softer" and less likely that events like this will happen as it accretes

 

[SpaceTiger]

Now, I have two questions, really. First, does my understanding of the very basic properties of accretion disks agree with the currently accepted models?

Which one? Unfortunately, we don't have a consensus accretion disk model at the moment. The situation you describe is consistent with simplest "thin disk" models that don't involve MHD or radiation pressure.

And second, is it possible for fusion to occur in the inner area of the disk?

The disk itself isn't dense enough to undergo nuclear fusion. Novae (runaway fusion reactions) can occur when disk material impacts the degenerate surface of a white dwarf, but the lack of a surface means you won't get this behavior with a black hole.