Collisionless and Collisional Effects on the Magnetorotational Instability in Accrection Disks

Details Collisionless and Collisional Effects on the Magnetorotational Instability in Accrection Disks Collisionless and Collisional Effects on the Magnetorotational Instability in Accrection Disks

Apr 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aps..apr.p7002s&link_type=abstract

American Physical Society, April Meeting, 2003, April 5-8, 2003 Philadelphia, Pennsylvania, MEETING ID: APR03, abstract #P7.002

Astronomy and Astrophysics

Astrophysics

Scientific paper

MHD turbulence resulting from the Magneto-Rotational Instability (MRI) is the most promising source of the efficient angular momentum transport needed to understand astrophysical accretion flows [Balbus & Hawley, Reviews of Modern Physics, 70, 1 (1998)]. We recently carried out a linear analysis of the MRI in a collisionless plasma using kinetic theory [Quataert, et.al. ApJ 577, 524 (2002)]. This is of interest for radiatively inefficient accretion flows onto black holes, or other cases where the collision frequency can be quite low. While the kinetic results are qualitatively similar to MHD, the kinetic growth rates can be either larger or smaller, depending on the parameter regime. The anisotropic pressure fluctuations possible in collisionless plasmas play an important role in enhancing the growth rate in some limits. Here we extend the linear kinetic calculation to include collisions, providing the ability to continuously move from the collisionless kinetic regime to the standard MHD regime. There is also a possible intermediate regime where collisions are faster than the MRI growth rate, so that the pressure anistropy is eliminated, but collisions are slower than the ion transit frequency v_ti k_|| so that wave-particle effects such as Landau damping can still occur. [Supported in part by NASA Astrophysics Theory Grant NAG5-12043.]

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