Analysing the Motion of Solar Wind Transients Using Stereo/Hi Observations

This thesis examines a technique used to study solar wind transients with the STEREO heliospheric imagers. We perform a manual extraction of profiles of transient events from elongation-time plots and apply this technique to the profiles. The technique assumes we are studying a point like object travelling at a constant speed and extracts the speed of the object and the direction it is travelling relative to the observer. We first examine the errors involved in performing the manual extraction of the profiles and from this conclude that any errors introduced are small and can easily be taken into account. Having examined the errors we then apply the technique to the two types of transient events, corotating interaction regions and coronal mass ejections. Corotating interaction regions have a spiral form and as such this technique should not work in determining their speed and position. However observations show that corotating interaction regions are made up of smaller scale transients which can be tracked. We were able to use this technique combined with in-situ measurements to track corotating interaction regions throughout the inner solar system. Coronal mass ejections are generally larger one-off events which can be more easily analysed by this technique. We examine several coronal mass ejections with the technique and confirm the measurements of speed and direction with in-situ measurements at Earth. We then discuss the assumptions involved in the technique and how they might affect the STEREO observations. We conclude that this technique can be used to track all types of solar wind transients and that future work should focus on further assessment of the assumptions.