HR: 1340h
AN: SA23A-0303    [Abstracts]
TI: Simulations of neutral wind shear effect on the equatorial ionosphere irregularities
AU: * Kim, J
EM: yegakjh@physics.utexas.edu
AF: Institute for Fusion Studies, The University of Texas at Austin, Austin, TX 78712 United States
AU: Chagelishvili, G
EM: georgech123@yahoo.com
AF: Center for Plasma Astrophysics, Abastumani Astrophysical Observatory, Ave. A. Kazbegi 2a, Tbilisi, 0160 Georgia
AU: Horton, W
EM: horton@physics.utexas.edu
AF: Institute for Fusion Studies, The University of Texas at Austin, Austin, TX 78712 United States
AB: We present numerical calculations of the large-scale electron density driven by the gradient drift instability in the daytime equatorial electrojet. Under two-fluid theory the linear analysis for kilometer scale waves lead to the result that all the perturbations are transformed to small scales through linear convection by shear and then damped by diffusion. The inclusion of the nonlinearity enables inverse energy cascade to provide energy to long scale. The feedback between velocity shear and nonlinearity keeps waves growing and leads to the turbulence. In strongly turbulent regime, the nonlinear states are saturated [1]. Since the convective nonlinearities are isotropic while the interactions of velocity shear with waves are anisotropic, the feedback do not necessarily enable waves to grow. The growth of waves are highly variable on k-space configuration [2]. Our simulations show that the directional relationship between vorticity of irregularities and shear are one of key factors. Thus during the transient period, the irregularities show the anisotropy of the vorticity power spectrum. We report the evolution of the power spectrum of the vorticity and density of irregularties and its anistropic nature as observed. The work was supported in part by the Department of NSF Grant ATM-0229863 and ISTC Grant G-553.
C. Ronchi, R.N. Sudan, and D.T. Farley. Numerical simulations of large-scale plasma turbulece in teh day time equatorial electrojet. J. Geophys. Res., 96:21263--21279, 1991.
G.D. Chagelishvili, R.G. Chanishvili, T.S. Hristov, and J.G. Lominadze. A turbulence model in unbounded smooth shear flows : The weak turbulence approach. JETP, 94(2):434--445, 2002.
DE: 2415 Equatorial ionosphere
DE: 2435 Ionospheric disturbances
DE: 2439 Ionospheric irregularities
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005