Ionospheric mid-latitude electron density background definition from CHAMP and Swarm satellite measurements under different solar conditions

In this work, a new method to define a background for the topside ionospheric electron density from satellite in-situ measurements is proposed as a useful tool for analysis of plasma density variations at LEO satellites heights. The method is applied to the data acquired by the Langmuir Probes onboard CHAMP satellite during the years 2004 and 2009, and the three Swarm satellites during 2016 and 2017 in the 15°-wide mid-latitudinal belt from 35°N to 50°N, and any longitude. CHAMP/Swarm in-situ measurements have also been used to check and compare such a new defined background with the one computed directly from IRI-2016 electron density output at satellite altitude. A general overestimation of the electron density from IRI during noon hours is highlighted, despite an underestimation of IRI with respect to Swarm-derived background for Swarm 2017 data is found as well, while the two backgrounds result more in agreement during night-time. Finally, the analysis of 2004 plasma data suggests that the IRI-2016 model could be used as a background during periods characterized by high levels of geomagnetic activity under high solar activity conditions.