Trapping of Dust Particles into Internal Resonances with the Inner Planets

Abstract

Trapping of dust particles into external resonances with the inner planets is a quite relevant phenomenon, which induces the formation of rings of dust around the planets' orbits, there being observational evidence of the Earth's resonant ring (Dermott et al., 1994). On the other hand, notwithstanding it is a less probable event, capture into internal resonance (diverging orbits) is predicted in numerical integrations of dust particles' orbits subject to Poynting-Robertson drag with one or two disturbing planets. Average theories, which give a good explanation for resonance trapping when the orbits are converging, do not allow capture for diverging orbits. Close approaches with the perturbing planet disallow the application of average theories, and numerical examples show that resonance trapping for internal resonances must have a chaotic origin. As expected from analytical theories, for the case of one disturbing planet, the particle's eccentricity decreases continually after capture and resonance is eventually broken. When two disturbing planets are present, however, there is not necessarily a decrease of the eccentricity, but it may increase, decrease or oscillate, although escape from resonance always occurs anyway.