Full-profile inversion of ionospheric radar data from Arecibo observatory

Incoherent scatter radar (ISR) technique is used to probe the ionosphere and measure the key state parameters of the ionosphere in thermodynamic equilibrium, including its electron density, ion densities and compositions, electron and ion temperatures, and the associated drift velocities of ionospheric particles via statistical inversion of the backscattered signal spectrum. In ISR probing different types of radar pulsing techniques can be chosen to establish some type of a compromise between range and frequency resolution of the measurements. In the “long pulse” mode, which is used to probe the topside ionosphere, range resolution is the primary difficulty that needs to be addressed during the inversion stage of the recorded spectral data. One approach to mitigate the “height mixing” effects involved in long pulse experiments is to conduct full profile analysis, which attempts to fit the spectra recorded from all radar ranges simultaneously with a large number of “unknowns” covering all the probed heights of the ionosphere at a high computation cost. In Holt et al. [1992], a lower-cost, spline based full profile approach interpolating the desired state parameters is described. The work described here uses a variant of the same approach applied to Arecibo long pulse ISR data collected during the September 2016 topside F-region ISR data campaign. Our description provides details of forward model construction, choice of spline parameters, the optimizing algorithm, and an independent electron density estimation procedure applicable when Te/Ti = 1. Lastly, our full profile estimation results are compared to results obtained by height-by-height inversions of the measured ISR spectra