Ionospheric field modeling from Swarm satellite data

Abstract:

Data based modeling of the magnetic field originating in the Earth’s ionosphere is challenging due to the multiple time scales involved and the small spatial scales of some of the current systems, especially the equatorial electrojet (EEJ) that flows along the magnetic dip-equator. We developed and algorithm, the Dedicated Ionospheric Field Inversion (DIFI) chain, that inverts a combination of Swarm satellite and ground observatory data at mid- to low-latitudes and provides models of the solar-quiet (Sq) and EEJ magnetic fields on the ground and at satellite altitude. The basis functions of these models are spherical harmonics in quasi-dipole coordinates and Fourier series describing the 24h, 12h, 8h and 6h periodicies, as well as the annual and semi-annual variations. A 1-D conductivity model of the Earth and a 2-D conductivity model of the oceans and continents are used to separate the primary ionospheric field from its induced counterpart. In this presentation we’ll report on various models obtained using the DIFI algorithm from the most recent Swarm data available. In particular, we’ll focus on how these models compare to earlier models such as CM4 derived from previous satellite missions, and to independent ground data not used in the inversion. We’ll also address the question of the magnitude of the Sq field on the night-side, which is of practical interest to the core field modeling community, as was apparent during the preparation of the last IGRF.