On the orbital evolution of the Lyrid meteoroid stream

A detailed analysis of the Lyrid video orbits from the EDMOND database is performed. Applying selective methods, the weighted mean orbit and mean geophysical parameters are derived. The occurrence of orbits with the semimajor axes smaller than 35 AU, in comparison with the value of 55 AU of the parent comet Thatcher, is about 80%, in the set of higher quality data of the Lyrids in the EDMOND database. The gravitational orbital evolutions of Thatcher and modelled particles ejected in five perihelion passages of the comet in the past are studied. Both, orbits of the comet and modelled particles, are under quite strong disturbing influence of Jupiter, Saturn and Earth. After the integration to the present, the mean theoretical radiants, the mean geocentric velocities and periods of activity of particles approaching the Earth's orbit were calculated. The mean orbits of the modelled streams of particles ejected from different perihelia match well the mean Lyrid orbit from the IAU MDC and the observed video Lyrids from the EDMOND database. The particles released in the two oldest simulated perihelion passages of the parent comet are most responsible for the occurrence of the Earth-crossing orbits with the semi major axes smaller than 35 AU, but no one below 20 AU. The influence of non-gravitational effects, mainly solar radiation, may shorten semimajor axis of a submilimeter particle with density of 0.3 g/cm(3) by more than half during an evolution of 50 000 years. A common influence of gravitational perturbations and non-gravitational effects can provide a dynamical way to the short-period orbits. However, this process is for millimeter and larger particles (video and photographic) less effective. (C) 2015 Elsevier Ltd. All rights reserved.