Simulation of Es Layer Modulated by Nonlinear Kelvin Helmholtz Instability

In this study, a two-dimensional numerical model of the nonlinear Kelvin-Helmholtz (KH) instability is used to investigate the nonlinear evolution processes of the ion layer, which is associated with the middle and low latitude E region irregularities. Based on simulation results, the two-stage process in the evolution of the nonlinear KH instability is found in KH vortex morphology. The simulated nonlinear KH instability process presents multiple striation structures, including horizontal structures of the primary ion layer vortex with a size of a few kilometers and the secondary KH vortex with a size of 2 km. The polarization electric field is induced in the horizontal structure of the sporadic E (Es) layer associated with the vortex structure of neutral wind. The polarization electric field presents a similar tendency to the quasi-periodic vortex structure. The horizontal distorted Es layer structure and anomalously large polarization electric field can provide the initial condition and lead to plasma instability, which can further develop to meter-scale irregularities of QP echoes.