THE LOCATION OF LINEAR SECULAR RESONANCES FOR SEMIMAJOR AXES SMALLER THAN 2 AU

In this paper, we present the location of lineal secular resonances in the region of semimajor axes a less than 2 AU, where many near-Earth asteroids (NEAs) are or shall be found. The results have been obtained by an automatic procedure using a seminumerical method valid also for high inclinations i of the asteroid and in the case of libration of t he perihelion argument (Kozai resonance). The positions of the secular resonances in the plane (a, i) show that the region of I-be inner pla nets is dynamically very complex: all the resonances (with the inner a nd the outer planets) are present and some of them even overlap, This shows that many secular perturbations and non-negligible orbital varia tions of small bodies can occur in this region. Indeed, some effects h ave already been found by numerical integrations, Therefore, a dynamic al model considering only the effects of close encounters with planets to study the evolution of NEAs is oversimplified and must take into a ccount the secular perturbations and resonances which appear to be num erous and relevant in the region where NEAs evolve. (C) 1997 Academic Press.