1202.4005 (Jason P. Byrne)
Jason P. Byrne
Solar coronal mass ejections (CMEs) are large-scale eruptions of plasma and
magnetic field from the Sun into the corona and interplanetary space. They are
the most significant drivers of adverse space weather at Earth and other
locations in the heliosphere, so it is important to understand the physics
governing their eruption and propagation. However the diffuse morphology and
transient nature of CMEs makes them difficult to identify and track using
traditional image processing techniques. In this thesis the implementation of
multiscale image processing techniques to identify and track the CME front
through coronagraph images is detailed. An ellipse characterisation of the CME
front is used to determine the CME kinematics and morphology with increased
precision as compared to techniques used in current CME catalogues, and efforts
are underway to automate this procedure for applying to a large number of CME
observations for future analysis. It was found that CMEs do not simply undergo
constant acceleration, but rather tend to show a higher acceleration early in
their propagation. The angular width of CMEs was also found to change as they
propagate, normally increasing with height from the Sun. However these results
were derived from plane-of-sky measurements with no correction for how the true
CME geometry and direction affect the kinematics and morphology observed. With
the advent of the unique dual perspectives of the STEREO spacecraft, the
multiscale methods were extended to an elliptical tie-pointing technique in
order reconstruct the front of a CME in three-dimensions. Applying this
technique to the Earth-directed CME of 12 December 2008 allowed an accurate
determination of its true kinematics and morphology, and the CME was found to
undergo early acceleration, non-radial motion, angular width expansion, and
aerodynamic drag in the solar wind as it propagated towards Earth.
View original:
http://arxiv.org/abs/1202.4005
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