Kinetic Effects of Intense E-Fields on Plasmas and Large-scale Simulations of the Farley-Buneman Plasma Instability in the Auroral Electrojet

Geomagnetic storms drive intense electric fields through the high-latitude E-region of the ionosphere, creating intense currents called electrojets. These fields drive the Farley-Buneman (FB) and enhance the gradient drift (GD) plasma instabilities. These instabilities then modify the conductivities and temperatures of the auroral electrojet with consequences for the entire magnetosphere-ionosphere-thermosphere (MIT) system. To quantify the kinetic effects of strong E-fields on the E-region plasma, we perform 3D plasma simulations using EPPIC — the electrostatic parallel particle-in-cell simulator. This shows that strong electric fields distort the shape of the ion velocity distribution function. We compare our simulations with a new analytic theory of distorted distribution functions. We also perform large-scale 3-D EPPIC simulations to model a section of the auroral electrojet that spans many kilometers vertically, such that ion-neutral collision rates change substantially along this direction. Until these simulations, all PIC simulations modeled small regions, assuming spatially constant collision rate. These simulations show how FB turbulence varies in a spatially inhomogeneous system. This will give insight into how small-scale plasma turbulence impacts the evolution of the auroral electrojet and should allow researchers to better interpret diagnostics.