Nonlinear dynamics of kink‐tearing modes and their interaction with the current profiles in a reversed‐field pinch

New insight in the nonlinear and quasilinear dynamics of kink‐tearing modes in reversed‐field pinches (RFP’s) is obtained by simultaneous measurements of the evolution of current profiles and associated m=1 helical mode spectra in the Extrap T1 RFP [Nucl. Fusion 34, 427 (1994)]. Results concerning near single helicity states, m=0 mediated m=1 spectral broadening and cascade, together with the associated relaxation dynamics, are reported. The role of phase locking, between the nonlinearly interacting modes, in the pinch dynamics is also discussed.