The activity of the 2004 Geminid meteor shower from global visual observations

Abstract

A comprehensive set of 612 h of visual meteor observations with a total of 29 077 Geminid meteors detected was analysed. The shower activity is measured in terms of the Zenithal Hourly Rate (ZHR). Two peaks are found at solar longitudes and with ZHR = 126 ± 4 and ZHR = 134 ± 4, respectively. The physical quantities of the Geminid meteoroid stream are the mass index and the spatial number density of particles. We find a mass index of s≈ 1.7 and two peaks of spatial number density 234 ± 36 and 220 ± 31 particles causing meteors of magnitude +6.5 and brighter in a volume of 109 km3, for the two corresponding ZHR maxima. There were 0.88 ± 0.08 and 0.98 ± 0.08 particles with masses of 1 g or more in the same volume during the two ZHR peaks. The second of the two maxima was populated by larger particles than the first one. We compare the activity and mass index profiles with recent Geminid stream modelling. The comparison may be useful to calibrate the numerical models.

Resonant behavior of comet Halley and the Orionid stream

“…3) of these zones. Our simulations match the observed ranges (207-210°) of solar longitude and outburst times (Trigo-Rodríguez et al 2007;Arlt et al 2008;Kero et al 2011; IMO Records) for these outburst years very well. Even though the uncertainties in semimajor axis (to directly compare with theoretical values in our calculations) of observed meteoroids from these highly successful observations are quite high (which is the typical case for all meteor observations, especially when the semimajor axis itself is high), the matching of outburst time frames and solar longitudes from these papers itself is a very effective way of comparing the orbital evolution of resonant meteoroids with real observations.…”

“…Past observations (Millman 1936;Lovell 1954;Imoto and Hasegawa 1958;Rendtel and Betlem 1993;Dubietis 2003;Rendtel 2007;Trigo-Rodríguez et al 2007;Arlt et al 2008;Spurny and Shrbeny 2008;Kero et al 2011) of Orionids have shown enhanced meteor activity in some particular years. Previous interesting works (Rendtel 2007;Sato and Watanabe 2007) have highlighted the significance of 1:6 MMR in explaining the outburst in 2006.…”

“…As there is a long record of observations for Orionids (Rendtel 2008), the same pattern could be compared and justified. The maximum ZHR in 2007 was about 80 (Arlt et al 2008), whereas in 1993, it was about 35 (Rendtel and Betlem 1993); cf. normal rates of 20-25.…”

“…The ejection epochs for 1:6 resonant meteoroids, which caused continuous enhanced activity in 2007, 2008, 2009, and 2010(Trigo-Rodríguez et al 2007Arlt et al 2008;Kero et al 2011;IMO Records) are also given in Table 1. These ejection years correspond to the time when the comet itself was 1:6 resonant.…”

“…It is interesting to note that the zenithal hourly rates (ZHR) of Orionids are nonuniform (Miskotte 1993;Rendtel and Betlem 1993;Rendtel 2007Rendtel , 2008Trigo-Rodríguez et al 2007;Arlt et al 2008;Kero et al 2011; International Meteor Organization Records) with respect to each year. Many previous works have discussed the active role of mean motion resonances (MMR) in the dynamical evolution of various meteoroid streams (e.g., Asher et al 1999;Emel'yanenko 2001;Asher and Emel'yanenko 2002;Ryabova 2003Ryabova , 2006Jenniskens 2006;Vaubaillon et al 2006;Jenniskens et al 2007;Christou et al 2008;Soja et al 2011), and consequent year-to-year variations in shower activity.…”