[P-CG21] Planetary Magnetosphere, Ionosphere, and Atmosphere

[PCG21-P01] Collisional acceleration of Mercury's sodium exosphere in MMIV-produced clouds

*Naoki Terada¹, Kaori Terada¹, Yohei Miyake² (1.Graduate School of Science, Tohoku University, 2.Graduate School of System Informatics, Kobe University)

Keywords:Mercury, Exosphere, DSMC

Although the tenuous atmosphere (exosphere) of Mercury is basically collisionless, it can be locally and transiently in a collisional regime in vapor clouds produced by meteoroid impact vaporization (MIV) or micro-meteoroid impact vaporization (MMIV). For the typical size and impact velocity of micro-meteoroids from Jupiter-family comets, the spatial and temporal scales of the collisional clouds are so small, on the order of meters and milliseconds, respectively, that the effect of collisions in the vapor clouds on the velocity distribution of the background exosphere has been often ignored in previous studies. In this study, we evaluate a cumulative effect of collisions in the MMIV-produced clouds on the velocity distribution of exospheric molecules using a Direct Simulation Monte-Carlo (DSMC) model. We will discuss possible modifications of the distribution of Mercury's sodium exosphere and its dependence on the true anomaly angle.