Unstable regions (striped) for the cases of (a) the plasma beta at the midplane ﹩\beta _{c}=100﹩ and (b) ﹩\beta _{c}=1000﹩ for the fiducial model (same as in Fig. 1). The dotted curve denotes the scale height of the disk, ﹩z=H( r) ﹩. In the region above the curve ﹩\lambda _{\mathrm{ideal}\,}/ H=1﹩, the instability does not effectively work because the wavelengths of the unstable modes are larger than the scale height of the disk. The region below the curve ﹩\lambda _{\mathrm{res}\,}/ H=1﹩ is stable because the magnetic dissipation is effective and corresponds to Gammie’s (1996) "dead zone."