Nonlinear coherent structures associated with drift-modes in a sheared magnetic field and an external sheared flow are studied analytically. Results show that there is a possibility of a dipole-like structure encapsulating a vortical flow at the centre. Stability of such a solution is investigated near the core where it has an elliptical shape. There is a significant growth of secondary modes for large as well as small ellipticity. Such secondary instabilities can act as a sink of vortex energy and thereby help in our understanding of nonlinear saturation of low-frequency instabilities.
展开▼
