Molecular ion composition measurements in the F1 region at Arecibo

The molecular ion composition in the F1 region is extremely difficult to measure with incoherent scatter (IS) radars because of the temperature/ion composition ambiguity in the shape of the incoherent scatter ion line spectrum. In practice, this means that a nonlinear least squares fitting (LSF) analysis of IS ion line data in this region can find different combinations of ionospheric parameters to be equally good fits. The only way to mitigate this problem is to add additional information to reduce the number of unknown parameters that need to be determined by the nonlinear least squares fitting. Following the concept originally reported by Waldteufel (1971), we have implemented a technique to combine the very precise electron density information in the plasma line with very accurate ion line spectra to measure the F1 region molecular ion composition. In this study, we describe the technique and show the first results from this method.