Seasonal variations in the north toroidal sporadic meteor source

Abstract

Determining the origins of the sporadic meteoroid sources helps determine their current properties. We have analyzed four years of orbital radar data, looking at how the rates, radiants, and orbits of meteoroids in the north toroidal sporadic source change throughout the year. Twelve broad radiant concentrations, separated in either time or radiant location, are identified. Six are broad distributions associated with more focused shower activity, and six are not associated with major showers. Four of the six concentrations not associated with showers have been named Toroidal, Toroidal A, Toroidal B, and Toroidal C, because of their constant location at the north toroidal centre. The other two, which appear close to the north toroidal source and drift toward the helion and antihelion sources respectively, have been named the Helion Arc and the Antihelion Arc. The twelve radiant concentrations generally last for more than ten degrees solar longitude, and those which may have a single parent are likely composed of orbitally evolved material.