Centrifugal effects and the Kelvin-Helmholtz instability in coronal cavities

It is proposed that the formation of the morphology of solar magnetic cavities and of the topology of their magnetic fields at a certain stage of their evolution (a decay of a quasi-uniform, rotating, magnetized cylindrical layer into rings, followed by their deformation and the generation of internal fine structure etc.) can be attributed to the excitation of a shear-centrifugal-resonance instability. The calculations show the existence of two families of unstable modes: resonance-gyroscopic modes due to the rotation of the layer and fast magneto acoustic waves propagating outside the layer and resonating in phase with intra-layer perturbations. Both families contain a large number of unstable waveguide harmonics, with the superposition and interaction of these harmonics being responsible for the extremely complex structure of coronal cavities.