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\centerline{\bf A Numerical Analysis of the Process of Capture into Resonance}
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\centerline {\bf Rodney S. Gomes (Observat\'orio Nacional - Brazil)}
\centerline {\bf Alexandre Y. Miguelote (Observat\'orio Nacional - Brazil)}

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The problem of capture into resonance, when a nonconservative force is present, has been
extensively studied be many authors. Probabilities of capture into resonance have been
given an analytical formulation for the case of adiabatic processes. However when
adiabaticity is not present, the trapping phenomenon is poorly understood. We here study
through several numerical simulations how capture is achieved for nonadiabatic processes.
We assume a planar restricted 3-body problem and start the numerical integration of the
orbits of several particles subject to Poynting-Robertson drag near the 2:3 (exterior)
resonance with the primary (with the Earth's mass and a circular orbit at 1AU). A strong
dependence on the initial mean longitudes is observed. Slightly changing the initial
semimajor axis, the proportion of captured particles to noncaptured particles varies
considerably. A good test for the understanding of the trapping process is the plotting
of the eccentricity and the resonant angle $(\phi)$ for the exact time when $\dot \phi=0$
for the first time and the comparison of the points so obtained which are associated to
captured particles to those which are associated to noncaptured particles.

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