Numerical considerations in the simulation of equatorial spread F

Abstract

The ionospheric irregularities known as equatorial spread F (ESF) have drawn great attention in decades due to their disruption of communications and navigation systems. ESF is generally attributed to Rayleigh-Taylor instability, but there are still many remaining issues about its formation and evolution. Numerical simulations have been widely used to study such a phenomenon due to the complex nonlinear evolution of ESF. A two-dimensional ESF model was developed in this work and a series of experiments were conducted to study the effects of grid resolution and numerical diffusion on idealized ESF simulation. It was found that advection schemes with the total variation diminishing (TVD) property are preferred for preventing spurious oscillations which occur near the steep density gradients in the ESF. On the other hand, schemes with low diffusion are also desirable in order to model complicated dynamic structures of the ESF. Moreover, numerical experiments suggest that some of the secondary instabilities in idealized ESF simulations, although with morphological similarities, are possibly initiated by numerical seeding, which may differ from the observed evolution of secondary ESF.