Simulations of Toroidal Current Drive Without External Magnetic Helicity Injection

It is shown by three-dimensional magnetohydrodynamic simulations that the toroidal current J_z can be induced by a process of relaxation without helicity invariance under no external magnetic helicity injection. It is shown that the magnetic helicity is induced during relaxation and it is passively determined as a result of the time evolution of the dynamical system. Numerical results suggest that the basic process for the toroidal current drive during relaxation is the nonlinear energy transfer from the toroidal magnetic energy to the poloidal one under the intervention of the kinetic energy. It is demonstrated that the self-organization to the lower eigenmode with a larger scale structure occures during relaxation