  Differentially rotating plasma disks, around compact objects, that are
imbedded in a ``seed'' magnetic field are shown to develop vertically localized
ballooning modes that are driven by the combined radial gradient of the
rotation frequency and vertical gradients of the plasma density and
temperature. When the electron mean free path is shorter than the disk height
and the relevant thermal conductivity can be neglected, the vertical particle
flows produced by of these modes have the effect to drive the density and
temperature profiles toward the ``adiabatic condition'' where
$\eta_{T}\equiv(dlnT/dz)/(dlnn/dz)=2/3$. Here $T$ is the plasma temperature and
$n$ the particle density. The faster growth rates correspond to steeper
temperature profiles $(\eta_{T}>2/3)$ such as those produced by an internal
(e.g., viscous) heating process. In the end, ballooning modes excited for
various values of $\eta_{T}$ can lead to the evolution of the disk into a
different current carrying configuration such as a sequence of plasma rings.
