Drivers of the variability of ionospheric plasma observed by the Swarm satellites in low Earth orbit

The ionosphere is a highly complex plasma containing electron density structures with a wide range of spatial scale sizes. Large-scale structures with horizontal extents of tens to hundreds of km exhibit variation with time of day, season, solar cycle, geomagnetic activity, solar wind conditions, and location. Whilst the processes driving these structures are well understood, the relative importance of these driving processes is a fundamental, unanswered question. These large-scale structures can also cause smaller-scale irregularities that arise due to instability processes and which can disrupt trans-ionospheric radio signals, including those used by Global Navigation Satellite Systems (GNSS). Ionospheric effects pose a substantial threat to the integrity, availability and accuracy of GNSS services. Strategies to predict the occurrence of plasma structures are therefore urgently needed.
Swarm is ESA's first constellation mission for Earth Observation (EO). It initially consisted of three identical satellites (Swarm A, Swarm B, and Swarm C), which were launched into Low Earth Orbit (LEO) in 2013. The configuration of the Swarm satellites, their near-polar orbits and the data products developed, enable studies of the spatial variability of the ionosphere at multiple scale sizes. The technique of Generalised Linear Modelling is used to identify the dominant driving processes of large-scale structures in the ionosphere at low, middle, auroral and polar latitudes. The statistical relationships between the ionospheric structures and the driving processes are determined in each region and the variations between regions are discussed, with a particular focus on the European sector. A predictive model for these ionospheric structures is currently under development.
This work is within the framework of the Swarm Variability of Ionospheric Plasma (Swarm-VIP) project, funded by ESA in the “Swarm+4D-Ionosphere” framework (ESA Contract No. 4000130562/20/I-DT).