Determination of the period of activity of meteoroid streams

A method for determination of the period of activity of meteoroid streams from photographic orbits is presented and discussed. It is also aimed at identifying stream members from marginal regions of activity. The search utilizes the Southworth-Hawkins D criterion. The primary separation of meteoroid stream members is based on the cumulative distribution of D. Variations of the orbital elements q, e, w and i with the solar longitude were derived from a set of selected orbits and applied to a search for the stream members from marginal regions of activity. Since the radiant is one of the most reliable parameters derived from observation, deviations of individual radiants from the stream radiant were taken as an additional criterion for a final stream membership classification. An application of the procedure to nine major streams led in the case of four streams to a probable assignment of meteors to the stream before or after the so far known “classical” period of activity: δ Aquarids (1), Perseids (8), Leonids (3) and Geminids (1). The significant number of Perseids found prior to July 23 (the onset of the stream activity) and the relatively small dispersion of their angular elements suggest that their assignment to the stream is rather reliable.