Study of storm-time ionospheric disturbances and irregularities using ionospheric data assimilation model

Abstract:

We report that assimilating ground-based and space borne GNSS observations into a coupled thermosphere-ionosphere model by using the ensemble Kalman filter (DART-TIEGCM) results in improved specification and forecast of eastward pre-reversal enhancement (PRE) electric field (E-field) during March 2015 magnetic storm period. Through data assimilation, not only the ionospheric plasma density, but thermospheric winds, temperature and compositions are also adjusted simultaneously according to their relationship to the ionospheric electron density. The improvement of dusk-side PRE E-field over the prior state is achieved primarily by intensification of eastward neutral wind. The improved E-field subsequently promotes a stronger plasma fountain and deepens the equatorial trough. As a result, the horizontal gradients of Pedersen conductivity and eastward wind are increased due to greater zonal electron density gradient and smaller ion drag at dusk, respectively. Such modifications provide preferable conditions and obtain a strengthened PRE magnitude closer to the observation.The assimilative outputs of ionospheric drivers are further utilized to the high-resolution regional ionospheric model, SAMI-3, for investigation of plasma bubble growths for pre-storm and storm conditions at various longitudes. As the upcoming COSMIC-2 mission is equipped with radio occultation observations of global electron density as well as in-situ ion density and velocity measurements at low latitudes, the observations will benefit the assimilation model by providing rich data source and to validation of plasma bubble occurrence forecasted by the assimilative model.