Simulations of Ion Thermal Farley-Buneman Instability in the Topside Electrojets

Linear theory has shown that ion thermal effects allow for Farley-Buneman instabilities (FBI) to occur at a wider range of altitudes than predicted for the adiabatic or isothermal FBI. This thermal Farley-Buneman instability (TFBI) is predicted to develop in topside electrojets (EJ) where the ion gyrofrequency exceeds the ion collision rate – a region where the FBI predicts no instability. We have performed the first simulations of this system using EPPIC — the electrostatic parallel particle-in-cell simulator — in order to verify the linear theory as well as to study the nonlinear behaviors. We have run a series of 2D simulations for different altitudes, ranging from the lower altitudes where the linear theory predicts high TFBI growth rates to higher altitudes where the linear theory does not predict TFBI growth. Simulation results show that TFBI develops at an even wider range of altitudes than predicted by the linear theory, hinting that detection of the instability by radars at these altitudes might be more possible than previously thought. The simulator also shows that in the nonlinear regime the high-altitude waves become longer in wavelengths as time goes on. A series of experiments at JRO are exploring these high-altitude EJ waves and we plan to compare these results to the theory and simulations. These results also pave the way for a future study of high latitude FB generated waves that span a range of altitudes with spatially varying collision rates. These waves impact current and energy flows through the E-region Ionosphere.