Development of a cometosheath at comet 67P/Churyumov-Gerasimenko

Context: The ionosphere of a comet is known to deflect the solar wind through mass loading, but interaction dependent on cometary activity. We investigate details this process at 67P using Rosetta Ion Composition Analyzer. Aims: This study aims compare and ions during two different time periods in mission. Methods: compared both integrated ion moments (density, velocity, momentum flux) velocity distribution functions for days, four months apart. were projected into coordinate system magnetic field direction averaged over three hours. Results: first case shows highly scattered H+ function. He2+ are somewhat scattered, less so, appear more like those H2O+ pickup ions. second characteristic evidence mass-loading, where species deflected, function not significantly changed. Conclusions: distributions case, when ions, indicative narrow cometosheath scale gyroradius. Thus, H2O+, with larger gyroradii, largely able pass cometosheath. An examination flux tensor suggests that all have significant non-gyrotropic component higher than mass-loaded case. Mass loading sufficient explanation so we assume bow shock formation.