The dynamics of spectral transfer in a model of drift wave turbulence with two nonlinearities

Abstract

The spectral transfer dynamics of two-dimensional (2-D) drift wave turbulence over a broad range incorporating long- and short-wavelength extremes is studied numerically in the context of dissipative trapped electron convective cell turbulence. The direction, locality, and isotropy of energy and enstrophy transfer in wave-number space are determined by examining energy and enstrophy transfer rates, the enstrophy generation rate, spectra, and the spectrum response to perturbative impulses. Energy transfer is characterized by two subranges, according to the dominant nonlinearity, and a dynamically complex crossover region dividing the subranges. In the long-wavelength E×B subrange, energy transfer is nonlocal and anisotropic, proceeding to shorter wavelengths with significant generation of enstrophy. In the short-wavelength polarization drift subrange, energy transfer is local and, in the absence of sources and sinks, is dominated by an inverse cascade, consistent with the near conservation of enstrophy on dynamical time scales. In the crossover region, there is isotropic nonlocal forward transfer, as well as cascading to long wavelength. A significant shift of the frequency spectrum peak in the crossover region is shown to result from the cross coupling of the two nonlinearities. The shift is in the electron diamagnetic direction and increases with increasing wave number, consistent with the behavior of the renormalized response function. The simulation model does not incorporate the effects of electron inertia, and therefore does not account for the feedback of the frequency shift on nonlinear mode stability. Nevertheless, the simulations provide numerical validation of many aspects of the accompanying analytical investigation [Liang et al., Phys. Fluids B 5, 1128 (1993)].