A Fluid Model for Estimating Minimum Scale Sizes in Ionospheric Plasma Cloud Striations.

摘要

We propose a fluid model for investigating the possibility that a small scale cut-off is present in plasma cloud striations due to particle diffusion. The model is two dimensional and perpendicular to the magnetic field, and assumes parameters applicable to the F region. The non-dimensionalized equations for the model show that the plasma motion is determined by initial plasma distribution and the value of an effective Reynolds number. Numerical simulations carried out for random phase initial conditions and maximum to minimum Pedersen conductivity ratio of 11 to 1 suggest that striation formation stops when the Reynolds number drops below about 400. We calculate a diffusion constant including electron-ion collisions, which can be dominant in high altitude releases. We then scale the results of the numerical simulation and conclude that the fluid model (without kinetic corrections) predicts a minimum scale size in the range 2.4-24 m for a typical choice of ionospheric parameters. These minimum scale sizes are in agreement with project STRESS rocket in situ measurements. (Author)