Contributions of nonlinear fluxes to the temporal response of fluid plasma

Abstract

Nonlinear energy fluxes are known to redistribute energy according to detailed conservation laws. In addition, the temporal response of plasma is altered by the linear reaction due to the nonlinear fluxes that are not involved in the transport of the energy. Simulations for three cases of the adiabaticity parameter alpha = 0.1, 1.0 and 10.0 are performed in relation to the Hasegawa-Wakatani model and the frequency alterations are found to be notable for kappa rho(s) > 0.5 where kappa is the Fourier scale and rho(s) is the ion gyro-radius computed at the electron temperature. The levels of the density fluctuation n((k) over right arrow) and the potential phi((k) over right arrow) get closer to each other as alpha increases and they are equal for alpha = 10. Yet, the frequencies are still discernible for alpha = 10.0. Non-transporting fluxes (NTFs) turned out to be anisotropic because the phase difference delta((k) over right arrow) between n((k) over right arrow) and phi((k) over right arrow) has symmetry so that cos delta((k) over right arrow) is isotropic in the Fourier space while sin delta((k) over right arrow) is odd in k(y). The NTF of the energy is approximated to be proportional to the gradient of the energy in the y direction of the Fourier space with the proportionality coefficient being dimensionally advecting velocity.