Instability and wave generation at the boundary regions of a comet

Waves and instabilities in plasma are seen throughout the Solar System.

At a comet, they are especially important as the main method for momentum transfer from the solar wind to the comet ionosphere.

In the region of the comet ionosphere where the solar wind has transferred the most momentum, waves and instabilities are known to exist, but have not been studied beyond individual cases.

We aim to fully characterize the process of momentum transfer by waves and instabilities using data from the Rosetta mission, which orbited comet 67P for two years with the Ion Composition Analyzer (ICA).

ICA could resolve the velocity distributions of the solar wind and cometary ions, necessary for full characterization of the waves and instabilities along with the pressure tensor.

We first find the best reference frame for analysis of the plasma pressure and velocity distributions, then use the ICA data in the reference frame to identify wave and instability signatures.

We will use a numerical dispersion solver to see which wave modes are generated by the observed distribitions to help identify waves.

With observations and simulations we can then find the momentum and energy transport between the solar wind and cometary ionosphere via these processes.

This work will provide insight into the physics at the boundary regions of a comet and energy transfer in space plasmas in general. The output of the project is also important for preparation for future comet missions such as Comet Interceptor.