Near Nucleus Dust Coma Analysis on the Base of In Situ GIADA Observations and Aspherical Dust Grain Model.

The new findings of the Rosetta mission at comet 67P/Churyumov-Gerasimenko (67P/CG) and the dust samples collected by the Stardust space probe at comet 81P/Wild revealed totally irregular dust particle shapes. Since August 2014 the Grain Impact Analyzer and Dust Accumulator (GIADA) has started capturing dust particles in the vicinity of comet 67P, measuring their momentum, optical cross section, speed and mass. Such unique, closest ever to a comet nucleus in situ dust dynamical measurements were never done before. We report the aspherical dust dynamics by means of numerical simulations and discuss its applicability to interpret the GIADA data. The translational and rotational motion of homogeneous, isothermal polygonal convex dust particles (close to ellipsoid of revolution with different axes aspect ratios) is studied under the influence of gravity, aerodynamic force and torque. The motion is numerically integrated in a wide range of physical parameters values, including those encountered at comet 67P/CG.