Files in this item
Files  Description  Format 

application/pdf Milla_Marco.pdf (6MB)  (no description provided) 
Description
Title:  Study of Coulomb collisions and magnetoionic propagation effects on incoherent scatter radar measurements at Jicamarca 
Author(s):  Milla, Marco A. 
Director of Research:  Kudeki, Erhan 
Doctoral Committee Chair(s):  Kudeki, Erhan 
Doctoral Committee Member(s):  Franke, Steven J.; Jin, Jianming; Makela, Jonathan J. 
Department / Program:  Electrical & Computer Eng 
Discipline:  Electrical & Computer Engr 
Degree Granting Institution:  University of Illinois at UrbanaChampaign 
Degree:  Ph.D. 
Genre:  Dissertation 
Subject(s):  Incoherent scatter radars
Remote sensing Ionospheric measurements 
Abstract:  In this dissertation, Coulomb collisions and magnetoionic propagation effects on the incoherent scatter radar measurements have been studied and analyzed in detail. The present study aims at modeling radar observations of the equatorial ionosphere carried out at the Jicamarca Radio Observatory (Lima, Peru) using antenna beams pointed perpendicular to the Earth's magnetic field B. A Monte Carlo procedure based on the simulation of charged particle trajectories in a magnetized plasma (with suppressed collective interactions) was developed to account for the effects of Coulomb collisions on the shape of the incoherent scatter spectrum. Statistics of simulated electron and ion trajectories, singleparticle ACF's, and associated Gordeyev integrals are utilized in the general framework of incoherent scatter spectrum models (e.g., Kudeki and Milla, 2006) to produce theoretical spectra for different plasma configurations. Our simulation method effectively extends the procedure of Sulzer and González (1999) into three dimensions and is valid for all magnetic aspect angles including the direction perpendicular to B. The 3D trajectories, randomized by Coulomb collisions, are described by a generalized Langevin equation with velocitydependent friction and diffusion coefficients taken from the standard FokkerPlanck collision model of Rosenbluth et al. (1957). A statistical analysis of the simulated trajectories shows that the ion motion is well modeled as a Brownianmotion process with Gaussian displacement distributions (and constant friction and diffusion coefficients), in which case, an analytical expression for the singleion ACF can be obtained (e.g., Woodman, 1967). However, the simulated electron motions do not fit a Brownian model because the electron displacement distributions in the direction parallel to B are sharper than a Gaussian. To account for these effects on our incoherent scatter spectrum model, a numerical library of electron statistics in an oxygen plasma (singleelectron ACF's) had to be developed. The library spans a set of densities, temperatures, and magnetic fields as needed for Jicamarca Fregion applications. The antenna beams used in perpendiculartoB radar observations at Jicamarca have angular widths of the order of a degree. Within this range of small magnetic aspect angles, different modes of magnetoionic wave propagation are excited. These characteristic modes vary from linearly polarized in the direction perpendicular to B (CottonMouton regime) to circularly polarized at aspect angles greater than 0.5 deg (Faraday rotation regime). In order to model the magnetoionic propagation effects on incoherent scatter radar measurements, a computer algorithm based on the AppletonHartree equation for electromagnetic wave propagation in a magnetized plasma was developed. Simulation studies show that magnetoionic propagation effectively modifies the shapes of the radar beams and does have an impact on the incoherent scatter radar measurements because the polarization of the incident and backscattered fields vary as they propagate through the ionosphere. A softtarget radar equation, which incorporates our collisional incoherent scatter spectrum and magnetoionic propagation models, is formulated to model the radar measurements collected at Jicamarca. Voltages detected by the radar antenna are represented as the beamweighted sum of ionospheric backscattered signals corresponding to the range of magnetic aspect angle directions illuminated by the antenna beam. This integration is carried out numerically using a finiteelementlike integration method that takes advantage of the slow variation of physical parameters in the direction transverse to the geomagnetic field. The resultant radar model is utilized in the inversion of ionospheric parameters in a threebeam radar experiment conducted at Jicamarca. The experiment interleaves radar observations with perpendiculartoB and offperpendicular antenna beams. The data model matches very closely the different features of the measured data; for instance, it predicts the enhancement of the measured power in the direction perpendiculartoB at ionospheric altitudes where the electron temperature is greater than the ion temperature. Fregion electron density and temperature ratio (T_e/T_i) estimates were obtained using a leastsquares inversion algorithm. The inversion results show a good agreement with ionosonde data, validating our model for incoherent scatter radar measurements. 
Issue Date:  20100820 
URI:  http://hdl.handle.net/2142/16746 
Rights Information:  Copyright 2010 Marco A. Milla 
Date Available in IDEALS:  20100820 
Date Deposited:  201008 
This item appears in the following Collection(s)

Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois 
Dissertations and Theses  Electrical and Computer Engineering
Dissertations and Theses in Electrical and Computer Engineering