The Variational Size Distribution of Dust on Comet 67P/Churyumov-Gerasimenko
I.-L. Lai1*, W.-H. Ip1,2, C.-C. Su3, J.-S. Wu3, J.-C. Lee4, Z.-Y. Lin2
1Institute of Space Sciences, National Central University, Taoyuan City, Taiwan
2Institute of Astronomy, National Central University, Taoyuan City, Taiwan
3Department of Mechanical Engineering, National Chiao-Tung University, Hsinchu City, Taiwan
4Department of Earth Sciences, National Central University, Taoyuan City, Taiwan
* presenting author:Ian-Lin Lai,
Because of the inclination of the rotational axis to the orbital plane and the orbital motion around the Sun, the sunlit regions on the nucleus surface of comet 67P/Churyumov-Gerasimenko (67P/C-G) shifted from the northern hemisphere to the southern hemisphere between August, 2014 and October, 2015. From the observations by the OSIRIS science onboard he Rosetta spacecraft, the source regions of the dust jets co-moved with the sunlit zones. During the perihelion passage, the strong outgassing activity in the southern hemisphere would lead to a significant ballistic transport of dusty grains to the northern hemisphere, in particular, the Hapi region. From our model calculations, a size screening effect might be present leading to the preferential recycle of dust particles with diameter (d) > 1 mm. In this event, the observed change of the slope of the cumulative dust size distribution from a value of γ ~ -4 in the outbound leg to a division to two slopes, i.e., γ ~ -2 for d < 1 mm to γ ~ -4 for d > 1 mm for the inbound leg could be explained. Some numerical examples will be presented to demonstrate this interesting dynamical effect.

Keywords: comets