Magnetic Shearing Instablilities in Accretion Disks
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**Session 21 -- Cataclysmic Variables, Dwarf Novae**
*Display presentation, Monday, 9, 1995, 9:20am - 6:30pm*

## [21.08] Magnetic Shearing Instablilities in Accretion Disks

*D. B. Curran and Ethan Vishniac (The University of Texas)*
We modify the force equations of a weakly magnetized disk to include
a diffusive term. This term is meant to approximate the effects of
nonlinear turbulence in the disk. The Velikhov-Chandrasekhar instability
appears as a local instability centered on a corotation radius. Imposing
the natural boundary condition that the instability vanishes far from
this radius eliminates the instability in the absence of noise or
dissipation. The diffusive term restores it. We combine our equations
to give a sixth order equation in the radial velocity. We examine
this equation for meanful singularities using a local Taylor expansion.
Real singularities in the complex frequency plane can imply the existence
of branch lines, which will permit the existence of localized solutions
corresponding to physically interesting instabilities. Having determined
the singularities we plot their behavior as a function of the diffusion
coeficient. Finally, we solve the original equation using the natural
boundary conditions and discuss the application of our solutions to
real, localized disk instabilities.

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