Fine Scale Structure in Cometary Dust Tails

Cometary dust tails often contain particularly striking fine structure. Unexplained alone by bulk dust properties, features such as the highly notable striae form due to as-yet unconstrained processes. This fine structure appears to be quite dynamic around perihelion, with little in the way of literature fully explaining what, how or why. This thesis focuses on the creation of this fine structure and its temporal evo- lution close to the sun. It shows the importance of the local conditions in the solar wind in explaining the behaviour of dust in a region of the heliosphere only recently probed by in-situ missions. To enable this analysis, a new technique has been developed – temporal map- ping – that displays cometary dust tails directly in the radiation beta (ratio of radi- ation pressure to gravity) and dust ejection time phase space. This allows for the combination of data sets and the removal of transient motion and scaling effects. The analysis makes use of serendipitous data from the SOHO and STEREO solar missions, and focuses on three comets, C/2006 P1 McNaught, C/2011 L4 Pan-STARRS and C/2002 V1 NEAT. At C/2006 P1, striae formation is directly shown through temporal mapping; the first observations of striae forming at any comet. A period of morphological change where striae undergo a reorganisation is also displayed and attributed to Lorentz forces caused by the comet’s dust tail crossing the heliospheric current sheet. The study of C/2011 L4 also reveals a period of striae reorganisation also cor- related with heliospheric current sheet crossings. Reorganised striae at both C/2006 P1 and C/2011 L4 display alignments that may be compatible with an additional solar wind influence. C/2002 V1 shows an interaction where a coronal mass ejection appears to affect dust tail orientation. The possibility of high solar wind pressure affecting dust morphology is ruled out. Changes in tail structure would therefore seem to be caused by Lorentz force effects