Joint inversion of CLP/ULP/LULP lag profiles measured in Arecibo Observatory during Sept 2016 ionosphere incoherent scatter experiment

A joint inversion procedure of Arecibo coded long pulse (CLP), uncoded long pulse (ULP), and longer uncoded long pulse (LULP) lag profile data from F-region altitudes is described. The procedure is based on a maximum likelihood approach applied to data collected during a measurement campaign conducted at Arecibo in Sept 23-26, 2016 period. The CLP lag profiles constitute relatively noisy measurements of the intrinsic ACF of ionospheric backscatter (at 300 m sampling intervals), but they are range-ambiguity-free in contrast to ULP (0.5 ms pulse length, 300 m sampling intervals) and LULP (1 ms pulse length, 600 m sampling intervals) based lag profiles — the latter can be viewed as less noisy intrinsic ACF’s contaminated by convolutional mixing. These three sets of lag profile matrices can be jointly inverted by making a proper use of the corresponding data covariance matrices as well as range mixing kernels: the misfit expression for each individual set is the L2-squared distance between the measured lag profiles and the range-mixed intrinsic ACF, weighted by the covariance matrix. The sum of three misfits are minimized for the most likely intrinsic ACF’s at all ranges covered using the Levenberg-Marquardt algorithm. The inversion procedure has been tested on the 10 min integrated observations from 12 PM AO LT on Sept 24, 2016, between 200 - 1200 km. The ion-line spectra are computed from the fitted intrinsic ACF, and ionospheric state parameters — electron density, ion composition, electron and ion temperatures — are extracted by ion-line spectral fittings. The valid range of parameters extends to ~ 1100 km, compared with < 600 km of the ones from CLP dataset.