AAS 200th meeting, Albuquerque, NM, June 2002
Session 71. Stellar Youth: Tomorrow's Degenerates
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

## [71.04] Internal Gravity Wave in Accretion Disks and its Coupling with Magnetorotational Instability

K. Noguchi (T-CNLS, LANL), H. Li (X-1, LANL), T. Tajima (SLAC, Stanford Univ.)

We study the stability of the internal gravity wave(IGW) in accretion disks. The IGW can excite in a disk because of its vertical stratification. Quite different from the case without shear, the IGW is destabilized by the flow shear, which also localizes the eigenmode in the radial direction. Our eigenmode analysis shows that the growth rate in pure hydrodynamical disk is quite small[Im(\omega)/\Omega=O(0.01)], where \Omega is the rotational period.\\ Despite the small growth rate in pure hydrodynamical disks, the coupling of the IGW with the magnetorotational instability(MRI) allow the unstable IGW mode to have larger growth rate[Im(\omega)/\Omega=O(0.1)] in the weak magnetic field regime(\omegaA/\Omega<0.1), accelerating the evolution of disks. As magnetic field grows by the MRI(\omegaA/\Omega>0.1), the MRI will take over the IGW instability and becomes a dominant instability.\\ As a conclusion, we sugget a new scenario for pure hydrodynamical disks and in weakly magnetized disks such as galactic and quasar disks, as well as stellar and protoplanetary disks. Unstable IGW mode and its coupling with MRI accelarate the evolution of accretion disks faster than the pure MRI, and the Parker instability can be turned on by the excited IGW mode in later stage, accelerating the structure and star formation in accretion disks.

The author(s) of this abstract have provided an email address for comments about the abstract: knoguchi@lanl.gov

Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.