Joint inversions of coded and uncoded long pulse F-region ISR returns

A joint inversion procedure of coded long pulse (CLP), uncoded long pulse (ULP), and longer uncoded long pulse (LULP) lag profile data from F-region altitudes based on a maximum likelihood approach is described.

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 and LULP (0.5 ms and 1 ms pulse length, respectively) 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 the three misfits is minimized for the most likely intrinsic ACF’s at all ranges covered using the Levenberg-Marquardt algorithm.

The procedure is applied to data collected during a measurement campaign conducted at Arecibo in September 23-26, 2016 period, 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, and ion bulk velocity — 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.