Numerical Simulations and Forecasts of Equatorial Spread F in the American Sector Based on ISR and HF Measurements

Abstract:

An ongoing effort to simulate plasma instability in the equatorial ionosphere leading to equatorial spread F (ESF) in the American sector is described. Ionospheric state parameters including plasma number density and vector drift velocity profiles have been measured at the Jicamarca Radio Observatory in campaigns in 2013 and 2014. Coherent radar backscatter from plasma irregularities has been recorded simultaneously, and images of the irregularities have been generated using aperture synthesis methods. A fully 3D numerical simulation of ionospheric irregularities, initialized and forced using parametrizations derived from measurements and empirical models, has been used in attempts to reproduce the ESF activity observed. Emphasis is placed on representing currents in the bottomside F region completely with the simulation. The simulations have been able to recover many of the features of the irregularities, although some important exceptions have been noted. ESF events in which the first appearance of radar plumes occurs either very early or very late cannot be reproduced in simulation and may be indicative of nonlocal influences. A new multistatic network of HF beacons is being deployed to estimate and track nonlocal influences on ionospheric stability. The network eploys PRN coding, Doppler discrimination, and interferometry and provides data suitable for inverse modeling. Preliminary results from the network will be presented.