Three-dimensional numerical simulation of equatorial F region plasma irregularities with bottomside shear flow

摘要

A three-dimensional numerical simulation of plasma density irregularities in the postsunset equatorial F region ionosphere leading to equatorial spread F (ESF) is described. The simulation advances the plasma number density and electrostatic potential forward in time by enforcing the constraints of quasi-neutrality and momentum conservation. The magnetic field lines are not modeled as equipotentials. Simulations are performed for cases with no background winds, with no background electric field or gravity, and with winds, a background electric field, and gravity all working in concert. The first run produced generalized Rayleigh Taylor (GRT) instability, and the second produced collisional shear instability (CSI). The combined run produced an instability which developed into an intense ESF event more quickly and with more realistic characteristics than the other two. Simulation results are compared with incoherent and coherent scatter radar data from the magnetic equator. A number of signature ESF characteristics are shown to be reproduced by the simulation.