Am. Hamza et Rn. Sudan, SUBGRID MODELING OF CONVECTIVE TURBULENCE IN WEAKLY IONIZED COLLISIONAL PLASMA BY RENORMALIZATION-GROUP ANALYSIS, J GEO R-S P, 100(A3), 1995, pp. 3669-3680
The equations governing the nonlinear evolution of density fluctuation
s in a low-pressure weakly ionized plasma driven unstable by the E x B
or gradient-drift instability were derived by Sudan and Keskinen (197
7, 1979) for addressing the electrostatic turbulence in the E and F re
gions of the Earth's ionosphere. We have developed a subgrid model sui
table for the numerical simulation of these equations which is closely
related to renormalized diffusion caused by small-scale fluctuation s
pectrum. ''Dynamical Renormalization Group'' (RNG) methods are employe
d to obtain the renormalized diffusion. This procedure computes the lo
ng-wavelength, long-time behavior of density correlations generated by
the evolution equation for the plasma stirred by a Gaussian random fo
rce characterized by a correlation function proportional to k(m) where
k is the wavenumber of the forcing function. The effect of small scal
es on the large-scale dynamics in the limit k --> 0 and infinite Reyno
lds number can be expressed in the form of renormalized coefficients;
in our case, renormalized diffusion. If one assumes the power spectra
to be given by the Kolmogorov argument of cascading of energy through
k space then one can derive a subgrid model based on the results of RN
G.