THEORY OF DRIFT-WAVE TURBULENCE

Toroidal ion temperature gradient (ITG) driven drift mode turbulence h as been analyzed analytically and numerically. By using weak nonlinear ity arguments and random phase approximation, dynamic and wave kinetic equations are derived. It is found that three different nonlinearitie s, namely E x B, convective and diamagnetic nonlinearities, play impor tant role in the turbulent spectral transfer. The power spectra of the weak ITG-mode turbulence are obtained analytically for \k\ much great er than 1 and \k\ < 1 ranges in the wave number space. It is shown tha t forward energy cascading due to convective and diamagnetic nonlinear ities will balance the inverse energy cascading due to E x B nonlinear ity at \k\ approximate to 1/rho(s) (k is wave number, rho(s), (c(s)/om ega(ci)) c(s) is the sound velocity and omega(ci) is the ion cyclotron frequency) and results in energy condensation at \k\ approximate to 1 /rho(s).