MHD simulation of the solar wind flow around the coma of comet Churyumov-Gerasimenko during Rosetta's flyby

Abstract

The magnetohydrodynamic (MHD) model of the interaction between the solar wind and a cometary ionosphere is applied to investigate certain peculiar features of the solar wind flow around comet Churyumov-Gerasimenko during Rosetta's flyby at this comet. The model accounts for photoionization of the neutral component of the cometary outflow and the resonance charge exchange between charged and neutral particles, together with the interplanetary magnetic field. It is found that the model performs well even beyond its apparent range of applicability and predicts the disturbed magnetic field in the comet's shock layer in agreement with the data measured onboard Rosetta. It can also offer explanation of the so-called solar wind void revealed by the onboard measurements. At the same time, the theoretical results concerning the contact surface (diamagnetic cavity boundary) are inconsistent with the experimental evidence. An analysis of the measured data and their comparison with the predictions allow one to conclude that in the case of 67P/CG the structure of the diamagnetic cavity is very peculiar in nature.