Structurally invariant plasmas

It is shown that it may be possible to operate devices in which plasmas are magnetically confined in such a way that the structure of the configuration remains constant during the discharge, i.e. the space and time variables are separable. Since MHD stability depends on structure only, it may be possible to realize circumstances under which the plasma is MHD stable throughout the discharge. Separation of the variables is possible only for certain functional forms of the appropriate transport coefficients, among which are the classical transport coefficients. A simple case where separation is possible has been calculated numerically and it appears that MHD stable configurations are among the solutions. (author)