Mass loading at 67P/Churyumov-Gerasimenko: a case study

TL;DR

This study analyzes how solar wind ions interact with a comet's atmosphere at 2.88 AU, revealing the dominant role of the solar wind electric field and the influence of an anti-sunward polarization electric field on ion dynamics.

Contribution

It provides new insights into the mass loading process and the electric field effects on cometary ion flow at low activity levels.

Findings

Cometary ion flow is mainly anti-sunward, not aligned with the convective electric field.

Solar wind electric field significantly influences cometary ion dynamics.

An anti-sunward polarization electric field adds to the solar wind electric field.

Abstract

We study the dynamics of the interaction between the solar wind ions and a partially ionized atmosphere around a comet, at a distance of 2.88 AU from the sun during a period of low nucleus activity. Comparing particle data and mag- netic field data for a case study, we highlight the prime role of the solar wind electric field in the cometary ion dynamics. Cometary ion and solar wind proton flow directions evolve in a correlated manner, as expected from the theory of mass loading. We find that the main component of the acceler- ated cometary ion flow direction is along the anti-sunward direction, and not along the convective electric field direc- tion. This is interpreted as the effect of an anti-sunward polarisation electric field adding up to the solar wind con- vective electric field.