On the estimation of E-region density profiles using IDA4D and COSMIC occultations

The E-region density is one of the key elements in the development of equatorial spread F. The linear growth rate of the generalized Rayleigh-Taylor instability depends heavily on the flux-tube integrated E-region Pedersen conductivity (e.g. Sultan,1996). Therefore, good estimates of E-region densities are necessary for a better understanding of ESF phenomenology. In this study, we investigate the estimation of E-region density profiles obtained with the Ionospheric Data Assimilation Four Dimensional (IDA4D). The profiles will be obtained by a) direct assimilation of radio occultation data into IDA4D and b) by using IDA4D F-region density results to assist the inversion of E-region profiles from occultation measurements. The results are compared with independent measurements of E-region density profiles made by the bistatic coherent scatter radar experiment in Peru (e.g. Hysell and Chau, 2001). Additionally, we present an analysis of the accuracy and variability of the E-region density predictions of the numerical models used to generate the background (initial state) ionosphere for IDA4D inversions (TIMEGCM and IRI).