Collisional electron cooling in the coma of comet 67P

In situ measurements from the dual Langmuir Probe (LAP) and Mutual Impedance Probe (MIP) onboard the Rosetta Plasma Consortium have shown that the electron environment in the coma of comet 67P/Churyumov-Gerasimenko is typically characterized by a pronounced bimodality, consisting of a cold component with energies below approximately 0.1 eV and a warmer component centered around 5 eV. This dual structure has often been interpreted using electron-neutral collisionopause concepts, which separate electron populations based on a prescribed spatial transition. While useful for qualitative interpretation, such approaches do not explicitly resolve the underlying electron energy distribution. By assuming that electrons and ions created simultaneously experience similar time-averaged neutral density fields it becomes possible to assess electron energy distributions semi-analytically via a continuous electron energy degradation model, grounded in laboratory work for electrons in water vapor. Preliminary results show that such a model reasonably well reproduces observed fractions of cold versus warm electrons in the coma of 67P during March 2016.