  Once a cometary plasma cloud has been created through ionisation of the
cometary neutrals, it presents an obstacle to the solar wind and the magnetic
field within it. The acceleration and incorporation of the cometary plasma by
the solar wind is a complex process that shapes the cometary plasma environment
and is responsible for the creation of boundaries such as a bow shock and
diamagnetic cavity boundary. It also gives rise to waves and electric fields
which in turn contribute to the acceleration of the plasma. This chapter aims
to provide an overview of how the solar wind is modified by the presence of the
cometary plasma, and how the cometary plasma is incorporated into the solar
wind. We will also discuss models and techniques widely used in the
investigation of the plasma environment in the context of recent findings by
Rosetta. In particular, this chapter highlights the richness of the processes
and regions within this environment and how processes on small scales can shape
boundaries on large scales. It has been fifteen years since the last book on
Comets was published and since then we have made great advances in the field of
cometary research. But many open questions remain which are listed and
discussed with particular emphasis on how to advance the field of cometary
plasma science through future space missions.
