Plasma line generation and spectral estimation from Arecibo Observatory radar data

Abstract

Incoherent scatter radar (ISR) signal spectrum is a statistical measure of Bragg scattered radio waves from thermal fluctuations of the electron density in the ionosphere. The ISR spectrum consists of up- and down-shifted electron plasma lines and a double-humped ion-line component associated with electron density waves with the governing dispersion relations of Langmuir and ion-acoustic waves, respectively. Such ISR spectral measurements can be conducted at the Arecibo Observatory, one of the most important centers in the world for research in radio astronomy, planetary radar and terrestrial aeronomy [Altschuler, 2002]. Although ISR measurements have been routinely taken at Arecibo since the early 1960s, full spectrum ISR measurements including the high-frequency plasma-line components became possible only very recently [Vierinen et al., 2017] as a result of critical recent upgrades in hardware configuration and computing resources. This thesis describes the estimation and analysis of the full Arecibo ISR spectrum using Arecibo line- and Gregorian-feed data collected with Echotec and USRP receivers in September 2016 and processed using GPU-based parallel programming technology. In spectral analysis the “CLEAN” algorithm is used to deconvolve the measured ISR spectrograms from frequency/height mixing caused by the finite pulse length effect. CLEANed spectrograms are subsequently fitted to a Gaussian spectral model for each height to extract an estimate of the plasma-line frequency for each height.