Satellite electron density variations derived with different backgrounds in different solar conditions

A new method to define a background for the ionospheric electron density (N_e) is presented, making use of mid-latitudes measurements under different solar conditions from the Langmuir probes onboard CHAMP and Swarm satellites. CHAMP measurements during the years 2004 and 2009, and Swarm observations during 2016 and 2017 have been considered in a belt of 15° in latitude from 30°N to 55°N, and from 0° to 360° in longitude. CHAMP/Swarm in situ measurements have been then used to check and compare this new defined background and the one computed directly from IRI-2016 N_e output at satellites altitude. Results of this comparison highlight a general overestimation of N_e from IRI during daytime, while a better agreement between the two backgrounds is found during nighttime. However, an underestimation of IRI with respect to Swarm-derived background is found for 2017 data. Finally, the analysis of 2004 plasma data suggests that IRI model can be used as background for high levels of geomagnetic activity.