High β toroidal configurations are discussed.Difficulties associated with the transition from a sharp boundary configuration to a configuration with a diffused current distribution, with regard to MHD equilibrium and stability may be avoided by going to configurations with internal separatrices.
Explosively unstable waves observed in an ion beam-plasma system. These waves are observed under the following two condition : (1) the drift velocity of the ion beam is nearly equal to the phase velocity of ion sound wave : (2) the frequencies of externally applied rf-field are neary equal to the ion plasma frequencies. The results are compared with a theory of explosive instability of single-triplet resonant interaction.