Ballooning Interchange Instabilities of Magnetized Plasmas under Gravitational Fields

The relation between the resistive ballooning mode and the ``universal'' type instability with gravitational field (simulating the magnetic field curvature) is discussed. It is shown that under appropriate assumptions, the instability of the ``universal'' type is an extension of the resistive ballooning mode if we replace the collision frequency in the resistive ballooning mode by the effective kinetic collision frequency kzve. The relative importance of these ballooning instabilities to toroidal plasmas is discussed.