An Inverse Theory Approach to Incoherent Scatter Drift and Temperature Estimation at the Jicamarca Radio Observatory
Bhattacharyya, Santanu
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https://hdl.handle.net/2142/81258
Description
Title
An Inverse Theory Approach to Incoherent Scatter Drift and Temperature Estimation at the Jicamarca Radio Observatory
Author(s)
Bhattacharyya, Santanu
Issue Date
1998
Doctoral Committee Chair(s)
Kudeki, Erhan
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Language
eng
Abstract
In this thesis we present a new spectral estimation technique which radically improves Equatorial E&ar;xB&ar; plasma drift measurements at low signal to noise ratios. The new technique exploits the long correlation times obtained when a radar beam is pointed perpendicular to the magnetic field. Using Doppler spectrum estimation techniques we are able to measure line-of-sight drifts with uncertainties as low as ∼0.5 m/s at signal to noise ratios as low as ∼0.1. In applying this technique to data obtained at the Jicamarca Radio Observatory we have discovered the existence of a westward traveling post sunset vortex which we report in this thesis. In an effort to improve our understanding of the width parameter of the incoherent scatter signal spectrum, we conducted careful measurements of the normalized incoherent scatter cross spectrum, termed coherence, for a pair of orthogonal baselines, one aligned parallel to and the other perpendicular to the B&ar; field at the Jicamarca Radio Observatory. In order to compare these measurements with theoretical predictions, we extended incoherent scatter theory to the realm of coherences. A very careful comparison between theoretical and measured spectra and theoretical and measured coherences has clearly established that the measured spectra and coherences are much narrower than those predicted by incoherent scatter theory. We speculate that an as yet unknown field aligned source could be the cause of the ambiguously low spectral widths obtained in our measurements. We have also found that our results exhibit a clear signature of East-West asymmetry. We present data to bolster these observations and comment on possible causes for these effects.
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