Radiation pressure forces on “typical” interplanetary dust grains

The radiation pressure force, that acts on dust in interplanetary space depends on size and composition of the particles. The knowledge of this effect is essential for the study of dust dynamics. Four models of “typical” interplanetary dust grains are constructed from common notions of their physical properties, and their possible parent bodies. The influence of radiation pressure forces on the particles is estimated by means of so-called β-values, that give the ratio of radiation pressure force to gravitation force in interplanetary space. The β-values and albedos are calculated using Mie theory for homogeneous and core-mantle spheres. The Maxwell-Garnett mixing rule is used to describe either the porosity of particle or the inclusion of another material. Derived albedos of mixed-material particles appear to be generally lower than those of grains consisting of pure, strongly absorbing substances, which has also influence on the radiation pressure forces. The calculations show that the assumption of extremely porous particles, often discussed as a description of cometary dust, leads to very high radiation pressure forces. Models applied for more compact particles, either of interstellar and asteroidal origin or produced by alteration of “fresh” cometary material show similar slopes of their beta values, which are lower than for the “young” cometary material. The study shows that only particles with masses m>10−10g can be assumed to behave dynamically (i.e. under influence of radiation pressure forces) like the “big” zodiacal particles (m>10−8g).