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 the perihelion argument (Kozai resonance). The positions of the secular resonances in the plane (a, i) show that the region of I-be inner planets is dynamically very complex: all the resonances (with the inner and the outer planets) are present and some of them even overlap, This shows that many secular perturbations and non-negligible orbital variations of small bodies can occur in this region. Indeed, some effects have already been found by numerical integrations, Therefore, a dynamical model considering only the effects of close encounters with planets to study the evolution of NEAs is oversimplified and must take into account the secular perturbations and resonances which appear to be numerous and relevant in the region where NEAs evolve. (C) 1997 Academic Press.