Coupling of Tearing Modes in Normal RFP Discharge

The dynamic process of the coupling of tearing modes in the normal RFP discharge, is studied with the help of 3-D MHD simulations. Almost of studies on the mechanism of the dynamo and the mode coupling have been carried out in the special operation mode “the deep reversal discharge” where the toroidal field at the wall is negatively increased. In this paper the dynamic process in the normal (ordinary) RFP discharge is reported. The process is as follows: The m =1 modes resonant near the plasma axis start growing in the initial stage. After growing enough, they interact with each other and the subsequent reconnection of magnetic field lines takes place. Consequently, m =0 modes are excited. In the normal RFP discharge, these couplings of tearing modes are frequently and periodically generated.