MODELING OF COMETARY EVOLUTION BY KINETIC-THEORY - METHOD AND FIRST RESULTS

Physical evolution of Jupiter family (JF) comets is considered as a si multaneous process of erosion and fading. Dynamical effects are Limite d to discrete changes of the perihelion distance, that result in chang es of the evaporation rate. Assuming that the JF comet population is i n a steady state, a distribution function of this population in the tw o dimensional phase space consisting of radius and active fraction of the nucleus surface is found as the solution of a set of kinetic equat ions, each one of them for a different perihelion distance. With use o f the distribution function some statistical properties of the comet p opulation, Like the total number of comets in the considered region of the phase space, the number of objects that evaporate or get dormant per unit time, etc., are obtained. The cumulative distribution functio n with respect to the absolute brightness is calculated and compared w ith the observed one as a check on the considered models.