M. D. Campbell-Brown

Model of the ablation of faint meteors

A model of meteor ablation in the atmosphere has been developed for meteoroids in the mass range 10 −12 kg to 4 × 10 −5 kg (size range 10 µm to 2 mm). The model builds on the classical model of meteor ablation, and adds a thermal fragmentation mechanism. The goal of the model is to characterize the physical structure (fundamental grain sizes) and chemical composition of meteoroids.

Annual variation of sporadic radar meteor rates

This paper describes a general approach for stochastic modeling of assets returns and liability cash-flows of a typical pensions insurer. On the asset side, we model the investment returns on equities and various classes of fixed-income instruments including short- and long-maturity fixed-rate bonds as well as index-linked and corporate bonds. On the liability side, the risks are driven by future mortality developments as well as price and wage inflation. All the risk factors are modeled as a multivariate stochastic process that captures the dynamics and the dependencies across different risk factors. The model is easy to interpret and to calibrate to both historical data and to forecasts or expert views concerning the future. The simple structure of the model allows for efficient computations. The construction of a million scenarios takes only a few minutes on a personal computer. The approach is illustrated with an asset-liability analysis of a defined benefit pension fund.

The 2005 Draconid outburst

Aims. We report the flux profile and mean orbit for meteoroids associated with an unexpected activity outburst from the Draconid meteor shower on 8 October, 2005. The primary aim is to define the characteristics of the outburst and establish the age of the associated meteoroids. Methods. Radar data from the outburst are used to define the flux profile and mass distribution for Draconid meteoroids at small meteoroid masses, while visual data are used to define the ZHR profile at larger masses. The radar recorded both single station and orbital data permitting orbits for many individual Draconid radar echoes as well as determination of a mean shower radiant. Results. The peak activity was centered at 16.1 hrs UT, (/to = 195°42 (J2000) solar longitude) with noticeably heightened radar activity lasting for a total of more than three hours. Based on the distribution of amplitudes for underdense Draconid echoes, the mean mass distribution index at masses of 10 -6 kg was found to be 2.0 ± 0.1. The equivalent hourly-binned radar ZHR was in excess of 150, while visual observations in the same intervals produced ZHRs of 40. The apparent radiant of the outburst was α = 256.9 ± 2.2°, δ = +56.6 ± 1.8°. Numerical modelling of radar-sized Draconids show that a significant number of meteoroids from the 1946 perihelion passage of 21 P/Giacobini-Zinner encountered the Earth over the interval 195°.23 λ ⊙ < 196°0 in 2005, centred about 195°50 Conclusions. The shower was rich in faint meteors, and therefore showed higher activity in radar data than in visual data alone. The duration of the outburst was very similar to past returns, while the mean radar stream orbit was somewhat different than previous measurements (the radiant differed by 6° in right ascension and 2° in declination) and also from the expected distribution of orbital elements for modelled 1946 meteoroids encountered in 2005.