Fragmentation model analysis of the observed atmospheric trajectory of the Tagish Lake fireball

Abstract

A recently published meteoroid fragmentation model (FM) was applied to observational data on the Tagish Lake meteoric fireball. An initial mass of 56,000 kg, derived from seismic and infrasound data by Brown et al.(2002), proved to be consistent with a very low value of intrinsic ablation coefficient of 0.0009 s^2km^(-2). The average residual of the best fit to the observed light curve was +/- 0.10 stellar magnitude. The apparent ablation coefficient varied from 0.0009 to 1.52 s^2 km^(-2), with an average value of 0.054 s^2 km^(-2) (determined by the gross fragmentation [GF] model). The FM found 33 individual fragmentation events during the penetration of the 56,000 kg initial mass of the Tagish Lake meteoroid through the atmosphere, with five of the events fragmenting more than 10% of the instantaneous mass of the main body. The largest event fragmented 88% of the mass of the main body at a height of 34.4 km. The velocity of the main body mass of 2660 kg at a height of 29.2 km (the last observed light) was 13.1 km/s. Strong fragmentation at heights lower than 29.2 km is very probable. The extreme fragmentation process of the Tagish Lake meteoroid puts its classification well outside the IIIB type in the direction of less cohesive bodies. The light curve could not be explained at all by making use of only the apparent ablation coefficient and apparent luminous efficiency.