Abstract
Aims.We present a multi-instrumental, multidecadal analysis of the activity of the Eta-Aquariid and Orionid meteor showers for the purpose of constraining models of 1P/Halley’s meteoroid streams.Methods.The interannual variability of the showers’ peak activity and period of duration is investigated through the compilation of published visual and radar observations prior to 1985 and more recent measurements reported in the International Meteor Organization (IMO) Visual Meteor DataBase, by the IMO Video Meteor Network and by the Canadian Meteor Orbit Radar (CMOR). These techniques probe the range of meteoroid masses from submilligrams to grams. Theη-Aquariids and Orionids activity duration, shape, maximum zenithal hourly rates values, and the solar longitude of annual peaks since 1985 are analyzed. When available, annual activity profiles recorded by each detection network were measured and are compared.Results.Observations from the three detection methods show generally good agreement in the showers’ shape, activity levels, and annual intensity variations. Both showers display several activity peaks of variable location and strength with time. Theη-Aquariids are usually two to three times stronger than the Orionids, but the two showers display occasional outbursts with peaks two to four times their usual activity level. CMOR observations since 2002 seem to support the existence of an ~12 yr cycle in Orionids activity variations; however, additional and longer term radar and optical observations of the shower are required to confirm such periodicity.
Highlights
Comet 1P/Halley is known to produce two annual meteor showers, the η-Aquariids in early May and the Orionids in late October
The interannual variability of the showers’ peak activity and period of duration is investigated through the compilation of published visual and radar observations prior to 1985 and more recent measurements reported in the International Meteor Organization (IMO) Visual Meteor DataBase, by the IMO Video Meteor Network and by the Canadian Meteor Orbit Radar (CMOR)
Individual activity profiles 6.1.1. η-Aquariids The η-Aquariids are generally active between L = 35◦ and L = 60◦, with highest rates recorded between L = 40◦ and L = 55◦
Summary
Comet 1P/Halley is known to produce two annual meteor showers, the η-Aquariids in early May and the Orionids in late October. They identified the 2:13 MMR as being responsible for the observed 1993 outburst and of a possible older outburst in 1916 Results of their simulations indicated several meteor outbursts due to particles trapped in the 1:6 resonance between AD 1436 and 1440, when Orionid outbursts were reported in ancient Chinese records The η-Aquariids is the strongest stream detected in specular backscatter by the Advanced Meteor Orbit Radar (Galligan 2000), which has a limiting sensitivity near +13 These observations support the idea that the η-Aquariids are rich in small meteoroids (Jenniskens 2006; Campbell-Brown & Brown 2015), with masses below 10−8 kg (Schult et al 2018)
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