Diurnal and Seasonal Variations of Sporadic Meteors Radiant Observed by Meteor Radars

Based on data collected from three meteor radars located at Mohe (MH, 53.5°N, 122.3°E), Wuhan (WH, 30.5°N, 114.6°E), and Ledong (LD, 18.4°N, 109.0°E), the diurnal and seasonal variations of the meteor counts, azimuth-zenith distributions of meteors, and sporadic meteor radiant are investigated. For the diurnal variation, meteor counts typically peak around 4 local time (LT) and reach their lowest levels near 17 LT, and the azimuth of the maximum meteor densities exhibits a clockwise rotation with LT. Such a characteristic is determined to be due to the domination of meteors from the helion direction during the daytime and from the antihelion direction during the nighttime. Additionally, three other meteor sources, north apex, south apex, and north toroidal have contributed to detections across all three radar sites. Distinct seasonal variations in meteor counts and azimuth-zenith distribution are observed at MH while such variations are less evident at WH and LD. The seasonal variation of the radiant distributions displays significant distinct characteristics among different latitudinal observations. These diurnal and seasonal variations can be well explained by the change in the relative positions of the five meteor sources in the radars' local frame of reference. Our study enhances our ability to predict the characteristics of meteor counts and azimuth-zenith distributions observed by meteor radar at any given time and location.