Leonid Meteoroid Orbits Perturbed by Collisions with Interplanetary Dust

Abstract

By analyzing high-accuracy Leonid orbits obtained from multiple-station meteor observations during the 1998 outburst and 1999 storm, we have detected the presence of meteoroids with peculiar orbits. These meteoroids are characterized by having a geocentric radiant nearly identical to the members of the storm that appeared with them but showing different orbital elements owing to their lower geocentric velocities. The changes in some orbital elements are significant and allow us to interpret the cause of such differences. Mainly, the semimajor axis and the eccentricity of these anomalous orbits are lower than expected for members of the dust trail or members coming from the background component linked to the annual stream. From these characteristics it is likely that these peculiar meteoroids suffered some perturbations on very short timescales. We have investigated several causes, including planetary perturbations, collisions, and radiative effects in order to explain the observed orbital changes. We conclude that these orbital changes can be explained by the loss of orbital energy close to the ecliptic plane. Such an effect can only be explained clearly by collisions of the original meteoroids with dust particles associated with the zodiacal dust cloud. We have applied this hypothesis in order to constrain some physical properties of 55P/Tempel-Tuttle cometary meteoroids.