Asymmetric toroidal flux generation due to phase locking of internally resonant tearing modes in the RELAX reversed-field pinch

Self-generation and sustainment of toroidal flux via a dynamo is one of the unique characteristics of the reversed-field pinch (RFP) configuration. In a small aspect ratio RFP machine RELAX, it has been observed that a sudden dynamo usually occurs at a localized toroidal location. This localized dynamo evolves in time, causing a toroidally asymmetric flux distribution. The degree of asymmetry depends on the location and propagation of the localized dynamo. It has been observed that the position where the localized dynamo occurs coincides with the position where the phases of the internally resonant tearing modes align. The phase alignment plays an important role in triggering a localized dynamo activity and in the formation of asymmetric toroidal flux distribution especially in deep-reversal plasmas in RELAX.