5.4 Orbital Evolution of Circum-Solar Dust Grains

The orbital evolution of circum-solar dust grains is obtained by numerical integration of the equations of motion which includes the grains’ interactions with the solar radiation field and the solar wind. Our past solution (Lamy, 1974) is improved by avoiding a classical approximation for the Poynting-Robertson term and leads to an important revision of the orbital behaviour. Results are presented for obsidian grains whose inward spiraling is stopped by the effect of sublimation.