Using nine years of Swarm magnetic field observations to estimate ionospheric electric current density through the curl-B technique

Besides the high resolution of measurements, one feature that distinguishes ESA Swarm mission from previous ones, also aimed at monitoring the Earth's magnetic field at Low Earth Orbit altitudes, is its configuration. We here take advantage of the nine years of geomagnetic field observations from Swarm satellites, to estimate the ionospheric F region current density. Specifically, we estimate the current density between Swarm A and B satellite altitudes, of about 510 and 460 km respectively, by calculating the curl of their Earth's magnetic field components.

This technique was first used in 2015 on a dataset of only seven months of vector magnetic data; because it was not possible to cover the entire local time range at the time, the corresponding mapping of ionospheric current density  was limited to two local nighttime intervals: before and after midnight. Seven years after the first application of this technique, we now use it on a more reliable and larger dataset and map the amplitude of the radial, meridional, and zonal components, as well as the total intensity of the ionospheric current density at all local times.