ESA Swarm Satellites Plasma Density Products: Comparison and Validation Against Incoherent Scatter Radars Observations

Abstract

The European Space Agency's Swarm mission has provided over a decade of continuous in situ measurements of the topside ionospheric plasma. With the release of various official plasma density products and the development of several calibration methods, selecting the most reliable data set has become an important issue for the scientific community. This study presents a comprehensive validation of Swarm plasma density products, including the standard Langmuir Probes (LP) harmonic and sweep modes, empirically corrected LP versions, physics‐based LP calibration—developed within SLIDEM (Swarm LP Ion Drift and Effective Mass) project –, neural network LP calibration (NNcor), and Faceplate (FP) observations, against ground‐truth observations from Jicamarca, Arecibo, and Millstone Hill incoherent scatter radars. By comparing both the statistical climatology and individual measurements at conjunctions, we demonstrate that the standard LP product generally underestimates plasma density by approximately 10%–20%, but with a consistent overestimation on the nightside at low solar activity. While empirical corrections reduce the mean bias, they do not significantly improve the dispersion of errors. Conversely, the neural network‐based NNcor data set, which calibrated LP observations to Swarm FP data, exhibits the best overall performance, achieving the highest correlation and minimizing residuals across different conditions. The physics‐based SLIDEM LP product also proves to be a robust alternative. We conclude that calibrated data sets, particularly NNcor and SLIDEM, are essential for accurate ionospheric modeling and should be preferred over standard products to avoid propagating instrumental biases into empirical models like the International Reference Ionosphere.