Coherent structures and their stability in ion temperature gradient turbulence

Periodic arrays of large scale-coherent vortices and their stability have been investigated, within the framework of eta(iota) turbulence, using two-dimensional fluid simulation in slab, geometry. These vortices, in combination with viscocity damping of small scales, contribute to the formation of a steady state in a I system with linearly unstable modes. The steady state comprises of a few vortex convective turn over times and seems to be fairly robust. It has been recognizid that a vortex chain, consisting of positive and negative vorticities, continues to move stably in the poloidal direction (along periodic direction). On the other hand, an initial isolated monopole vortex is unstable and leads to a long-lived stable dipolar structure after a, few vortex turnover periods. A variety of simple collisonal interaction processes among these coherent vortices have also been,explored numerically.