Resonance Type Instabilities in the Gaseous Disks of the Flat Galaxies III. The gyroscopical resonance type instability

The stability of thin homogeneous gaseous disk with step discontinuity of velocity and density profile has been investigated analytically in the limitary case of large compressibility and numerically at spatially separated velocity and density kinks. The expressions for reflection and transmission coefficients at the axisymmetrical vortex sheet are derived. The possibility of gyroscopical resonance type instability development in addition to Kelvin--Helmholtz and centrifugal instabilities is shown and its physical mechanism is clarified. It has been discussed the possibility of application of obtained results to the stability analysis of the gaseous disks of the real flat galaxies.