Plasma cloud late time striation spectra

摘要: In order to obtain striation power spectra and understand the nonlinear saturated state of gradient drift instability, which is believed be responsible for striations in plasma clouds coupled background ionosphere, a two-level (one cloud one ionosphere), two-dimensional numerical simulation has been performed. The taken F region, ionospheric level lower or E temperature zero at both levels. initially assumed Gaussian direction (y) uniform (x) ambient electric field, magnetic field z direction. initialized with random perturbations, high-resolution carried out over entire (x, y) mesh. linear phase simulation, grow on back side image appear ionosphere. characterized by pinching original perturbations within cloud, production secondary bubbling through front appearance large modal development shows that late times spectrum density fluctuations obeys law dependence k space. Specifically, x one-dimensional ∝ kx where nx ≈ 2–3 (for wavelengths between 0.6 12 km), y ky ny 2 100 km). This evolution favors long wavelengths, whereas theory our model system growth rate maximizes short wavelengths. Such inversion may explaining long-wavelength preferred scale size seen barium clouds.