Hydrodynamic instabilities in the tachocline driving by layer thickness variations and mean flow inhomogeneities

This paper presents the results of numerical experiments with the shallow water quasi-geostrophic model. These results were used to assess instability increments in the tachocline, caused by layer thickness variations and mean flow inhomogeneities. According to the calculations, the layer thickness variations and mean flow inhomogeneities lead to destabilization of differential rotation, even if the differential rotation profile is stable. The time of instability enhancement is strongly dependent on the amplitude and spatial structure of disturbances. Disturbances of the tachocline thickness and mean flow inhomogeneities may be due to penetrative convection cells, diffusion of the relic magnetic field and magnetic fields from the convection region.