When cometary dust particles are ejected from the surface they are accelerated because of the surrounding gas flow from sublimating ices. As these particles travel millions of kilometres from their origin into the solar system they produce the magnificent tails commonly associated with comets. During their long journey the dust particles transition through different regimes of changing dominant forces such as gas drag, cometary gravity, solar radiation pressure, and solar gravity. The transition and link between the different regimes is to this day poorly understood. There are two main reasons for this. Firstly, the problem covers a vast range in spatial and temporal scales that need to be matched taking into account multiple transitions of the force regime. Furthermore, observational data covering these large spatial and temporal scales for at least one comet and thus characterising it in great detail has been lacking until recently.
For comet 67P/Churyumov-Gerasimenko (hereafter 67P) a small number of large scale structures in the outer dust coma and tail have been found from ground based observations. Conversely ESA’s Rosetta mission has shown many small scale structures defining the innermost coma close to the nucleus surface. This disconnect between the observations on these different scales has yet to be understood and explained.
Solving this problem thus requires an interdisciplinary approach. This ISSI team shall bring together experts of the recent observational data from ground and in-situ of comet 67P as well as theorists that are able to model the dynamical processes over these different scales. By doing so we intend to answer some of the open questions that came out of the Rosetta mission and the accompanying ground based observations. The understanding gained about 67P will also be put in context by evaluating how it can be applied to furthering our knowledge of other comets.