On the Structure of the Halley Comet Meteor Stream

Twice every year the Earth passes through the meteoroid stream from Halley's comet producing the Orionid and Eta-Aquarid meteor showers. To study the stream development, the motion of 500 test particles released from the comet with ejection velocities calculated according to Whipple has been integrated over long periods assuming Jupiter to be the only gravitational perturbation. It was found that the stream cross-section in the ecliptic plane becomes highly elliptical within a few thousand years. This confirms the ribbon-like stream structure proposed by McIntosh and Hajduk which explains most of the observed features of the showers. Fine-structure features develop rapidly and are most apparent for more massive particles. The minimum age of the Orionid shower is about 3000 years.