Preliminary Numerical Study of the Outer Scale Size of Ionospheric Plasma Cloud Striations

Abstract

The one-level (one for the plasma cloud and neglect of cloud-background ionosphere interaction), two-dimensional fluid equations modeling striation development in large F region ionospheric plasma clouds have been numerically solved, by using an initial one-dimensional cloud geometry, for three different initial Pedersen conductivity gradient scale lengths L=3, 6, and 10 km. In the nonlinear regime, evidence is presented for an outer scale size of well-developed striations in a direction (y) perpendicular to the E × B drift (x) of the plasma cloud whose initial Pedersen conductivity varies only along the drift direction. The perpendicular outer scale size 2π/k0y is proportional to the initial gradient scale length L through a constant of order unity, i.e., k0yL/2π ≃1. In addition, for the three scale lengths L studied, the one-dimensional x power spectra ∝kx−n x with n x ≃2 for 2π/k x between 1 and 80 km, while the y power spectra ∝ky−n y with n y ≃2–2.5 for 2π/k y between 1 and 10 km. These results are consistent with recent experimental and theoretical studies of plasma cloud striations.