Activity of the Eta-Aquariid and Orionid meteor showers

TL;DR

This study analyzes multi-decadal observational data of Eta-Aquariid and Orionid meteor showers to understand their activity patterns, variability, and potential periodicities, aiding in refining models of 1P/Halley's meteoroid streams.

Contribution

It provides a comprehensive multi-instrumental analysis of shower activity, variability, and possible periodicity, improving understanding of meteoroid stream dynamics.

Findings

Eta-Aquariids are typically 2-3 times stronger than Orionids.

Both showers show multiple activity peaks with variable strength.

Evidence suggests a possible ~12-year cycle in Orionids activity.

Abstract

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. 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. The Eta-Aquariids and Orionids activity duration, shape, maximum zenithal hourly rates (ZHR) 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. 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. The Eta-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 year cycle in Orionids activity variations; however, additional and longer term radar and optical observations of the shower are required to confirm such periodicity.