Nondissipative kinetic simulation and analytical solution of three-mode equations of the ion temperature gradient instability

A nondissipative drift kinetic simulation scheme, which rigorously satisfie s the time-reversibility, is applied to the three-mode coupling problem of the ion temperature gradient (ITG) instability. It is found from the simula tion that the three-mode ITG system repeats growth and decay with a period which shows a logarithmic divergence for infinitesimal initial perturbation s. Accordingly, time average of the mode amplitude vanishes, as the initial amplitude approaches zero. An exact solution is analytically given for a c lass of initial conditions. An excellent agreement is confirmed between the analytical solution and numerical results. The results obtained here provi de a useful reference for basic benchmarking of theories and simulations of the ITG modes. (C) 2000 American Institute of Physics. [S1070-664X(00)0200 3-6].