Tau Herculids 2022: Rate, number density, population index and geometrical effects from visual data

Abstract

We analysed visual observation data of the Tau Herculids collected between 2022 May 28 and June 1. The population index for the entire sample is 2.4. For the pre-peak period we find r=2.57+-0.23, the peak period yields r=2.38+-0.06. The ZHR maximum of the 1995 ejecta from comet Schwassmann-Wachmann3 (SW3) is found at 69.450 deg solar longitude (May 31, 05h04mUT, +-5min) with a ZHR=55+-7, corresponding to a spatial number density ND of approx. 380 meteoroids larger than 10mg in a cube with 1000km edge length. An earlier maximum occurred at 69.207 deg solar longitude (centred May 30, 23h UT) with a ZHR=18+-3 and is tentatively associated with SW3-ejecta from 1892. Effects of the radiant shift due to the large zenith attraction of about 10 deg for the radiant close to the horizon are discussed.