Modeling the gradient drift and Kelvin-Helmholtz instabilities as generation mechanisms of mid-latitude ionospheric density Irregularities

Ionospheric irregularities have been observed in the mid-latitude ionosphere from space weather radar, GPS, and satellite data. They are small-scale structures in the plasma density created by various plasma instabilities, which are driven by combinations of plasma drifts, density gradients, and electric fields. Ionospheric processes producing the mid-latitude GPS scintillations are less understood due to the lack of numerical models that can explain their characteristics and distributions. In this work, the physics of the interaction between the gradient drift instability (GDI) and the Kelvin-Helmholtz instability (KHI) are explored in order to understand how they cause turbulence in the ionosphere. A better understanding of formation and development of ionospheric turbulence can provide insight on improving models of space weather, hence improving accuracy of communication signals. In order to study the formation and growth of ionospheric instabilities such as GDI and KHI, a 2D/3D electrostatic fluid model was developed that considers the equations representing continuity(mass conservation), temperature, and current closure(charge conservation). These form a system of nonlinear partial differential equations which are discretized and solved using several well-established numerical techniques, including the pseudo-spectral method, the Fourier transform, and the Runge-Kutta method. The numerical model will be used to study mid-latitude ionospheric phenomena, such as Subauroral polarization streams (SAPS), Polar Cap Patches, and mid-latitude ionospheric disturbances relevant to space weather radar observations. Numerical results are presented and compared to recent experimental observations.