**AAS 199th meeting, Washington, DC, January 2002**

*Session 60. Star Formation - Accretion and Outflow*

Display, Tuesday, January 8, 2002, 9:20am-6:30pm, Exhibit Hall
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## [60.18] Nonlinear Evolution of the Magnetorotational Instability in Weakly Ionized Accretion Disks: Effect of the Hall Term and Ohmic Dissipation

*T. Sano, J. M. Stone (Univ. of Maryland)*

The structure and evolution of accretion disks are largely
determined by angular momentum transport processes. One of
the most promising processes is MHD turbulence driven by the
magnetorotational instability (MRI). The nonlinear regime of
the MRI has been well studied in ideal MHD using numerical
simulations. However, in some astrophysical systems,
accretion disks are expected to be only partially ionized,
in which case non-ideal MHD effects must be considered.

In circumstellar (protoplanetary) disks around young stars
and in dwarf nova disks in quiescence, the Hall effect and
ohmic dissipation are important. Recently, linear analyses
of the MRI in the Hall regime has been presented by Wardle
(1999) and Balbus & Terquem (2001). The maximum growth rate
and characteristic wavelength of the MRI are strongly
modified by the Hall effect. Most interesting is that the
linear properties of the instability depend on the direction
of magnetic field.

We investigate the effect of the Hall term on the nonlinear
evolution of the MRI using 3D non-ideal MHD simulations. The
local shearing box approximation is used for the
calculations. The characteristics of the saturated turbulent
state, which determines the accretion rate, are found to
depend on the efficiency of the Hall term and ohmic
dissipation. We discus the conditions for significant
accretion rate in weakly ionized disks and apply the results
to the evolutionary scenarios for protoplanetary and dwarf
nova disks.

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