SELF-ORGANIZATION, ANOMALOUS RESISTANCE AND ANOMALOUS HEATING IN MAGNETIZED PLASMAS

The nonlinear dynamics and structure of plasmas with tightly twisted m agnetic field lines have been studied using a toroidal plasma device. Stepwise magnetohydrodynamic (MHD) relaxation occurs, resulting in a d iscontinuous change in the pitch of magnetic field lines. This discret e nature of the pitch stems from the instability of kink (torsional) m odes. The MHD relaxation stabilizes kink modes by selecting (self-orga nizing) appropriate pitches. The self-organized state displays the cha racteristic of a 'dissipative structure' in that it is accompanied by enhanced energy dissipation; the global resistance of the plasma curre nt is substantially enhanced. The magnetic energy, which is generated by the internal plasma current, first changes into fluctuation energy through the kink instability, and then it goes mainly to ion thermal e nergy through viscous dissipation of the fluctuating flow. The viscosi ty dissipates the fluctuation energy with conservation of helicity. Th e self-organization of the stabilized magnetic held is characterized b y the preferential conservation of the helicity.