  Coronal mass ejections (CMEs) are large-scale expulsions of plasma and
magnetic fields from the Sun into the heliosphere and are the most important
driver of space weather. The geo-effectiveness of a CME is primarily determined
by its magnetic field strength and topology. Measurement of CME magnetic
fields, both in the corona and heliosphere, is essential for improving space
weather forecasting. Observations at radio wavelengths can provide several
remote measurement tools for estimating both strength and topology of the CME
magnetic fields. Among them, gyrosynchrotron (GS) emission produced by
mildly-relativistic electrons trapped in CME magnetic fields is one of the
promising methods to estimate magnetic field strength of CMEs at lower and
middle coronal heights. However, GS emissions from some parts of the CME are
much fainter than the quiet Sun emission and require high dynamic range (DR)
imaging for their detection. This thesis presents a state-of-the-art
calibration and imaging algorithm capable of routinely producing high DR
spectropolarimetric snapshot solar radio images using data from a new
technology radio telescope, the Murchison Widefield Array. This allows us to
detect much fainter GS emissions from CME plasma at much higher coronal
heights. For the first time, robust circular polarization measurements have
been jointly used with total intensity measurements to constrain the GS model
parameters, which has significantly improved the robustness of the estimated GS
model parameters. A piece of observational evidence is also found that
routinely used homogeneous and isotropic GS models may not always be sufficient
to model the observations. In the future, with upcoming sensitive telescopes
and physics-based forward models, it should be possible to relax some of these
assumptions and make this method more robust for estimating CME plasma
parameters at coronal heights.
