A 13-year radar study of the η-aquariid meteor shower

Abstract

We measure the activity and orbital characteristics of the η-Aquariid meteor shower appropriate to meteoroids of 200 μm size (mass ≈ 5-10 μg) based on ~4 × 104 stream orbits measured by the Canadian Meteor Orbit Radar during the years 2002-2014. Significant activity from the stream is found to last from April 25-May 21 (λ⊙ = 35°-60°) with the shower detectable approximately one week on either side of these dates just above the median background. The radiant at peak activity (λ⊙ = 45.°5) is located at αg = 337.°8, δg = -0.λ6 and shows a consistent drift of Δαg = +0.°69, Δδg = +0.°60. The velocity of the stream throughout its active period remains within ≈1 kms-1 of Vg = 64.3 kms-1 found at the peak; however, there are indications this is an underestimate due to undercorrection for stream meteoroids having larger than average deceleration. The activity profile shows no mass dependence between μg to mg sizes, but a clear asymmetry with the slope of the ascending branch having B+ = 0.135 ± 0.003 and the descending branch B- = 0.078 ± 0.003. The average yearly equivalent radar-measured peak Zenithal Hourly Rate (ZHR) is 50-80 from 2002-2014, with outbursts in 2004 and 2013 exceeding ZHRs of 100. The mass index shows a minimum at the time of the flux maximum with 1.8 ≤ s ≤ 1.9.