Stability, Turbulence, and Gravitational Energy Release in Black Hole Accretion Disks
Aristotle Socrates (UC Santa Barbara) - November 5 at 12:00 noon
Fluid dynamical and spectral modeling of accretion onto a black hole has
advanced significantly over the last few decades. However, progress
towards understanding the mechanics of the flow and the spectrum which it
radiates has occurred separately, with little quantitative connection
between the two. Under the framework of radiation magnetohydrodynamics, I
will show that magnetized accretion disks are dynamically unstable to
photon bubble-like instabilities. I will discuss how these
radiation-driven fluid instabilities may alter the disk's vertical
structure and emergent spectrum. Also, I will consider how the
turbulence, which is required for angular momentum transport, affects the
thermal spectrum of the putative disk. Since the turbulent velocities of
the accretion flow may exceed the electron thermal velocity, bulk
Comptonization by the turbulent motions themselves, in other words
turbulent Comptonization, may serve as the radiation mechanism which
mediates gravitational energy release. Turbulent Comptonization provides
an intrinsic source of X-ray photons while giving observers the ability to
constrain properties of the turbulence itself.
The seminar will be held in 501 Campbell Hall.
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