Reevaluation of EISCAT plasma parameters during the May 2024 geomagnetic storm using O + ratios from AMIE-driven SD-WACCM-X

We present a reevaluation of EISCAT plasma parameters during the May 2024 geomagnetic storm, applying the ion composition from an AMIE-driven SD-WACCM-X simulation instead of the standard IRI model. This resulted in significant deviations of F1 region electron densities (up to 15 %), electron temperature (40 %), and ion temperatures (30 %) from the original analysis. Parameter uncertainties are also shown to be affected by the reevaluation (5 %–10 %). The correlations of parameter uncertainty, ion composition differences, and absolute ion composition profiles are investigated. It is shown that in the F1 region, the plasma parameter deviations are notably larger than the uncertainty range. Incorrect assumptions about the ion composition can have a significant impact on the accuracy of ISR measurements, which has important consequences for the possible application of ISR data in data assimilation. Advantages and disadvantages compared to previously presented approaches regarding the ion composition issue are discussed. The presented method allows to de-bias storm-time ISR measurements with standard analysis software. Whether a generally applicable empirical model, which would allow for de-biasing without additional incoherent scatter analysis, can be derived with the presented method remains to be investigated in the future.