Southern Hemisphere Meteor Stream Determinations

Abstract

Meteor orbits have been deduced from radio observations of meteor trails carried out at Adelaide (latitude 35� S.), using a combined multi-station continuous wave and pulse radar system operating at 27 MHz. Observations were made for one week each month during the period December 1968 to June 1969, and also during October 1969. The orbits of 1667 meteors have been determined down to a limiting radio magnitude of + 8. The data have been systematically searched for stream meteors, and the significance of minor associations has been appraised. Altogether 40� 4 % of the orbits were found to be associated with at least one other orbit, and 29� 8 % with two or more. Numerous minor streams with high inclination and low eccentricity have been found at deep, southern declinations from December to March, with little activity in this quarter during June and October. In addition to confirming several previously established cometary associations, a comprehensive search has indicated that 34 of the meteor associations found may be related to 17 comets. Associations between several long-period comets and low-eccentricity high-inclination streams appear to be indisputable, and they confirm the origin of at least some of the 'toroidal group' meteors, previously a matter of some doubt.