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BOLIDES PRODUCED BY IMPACTS OF LARGE METEOROIDS INTO THE EARTH'S ATMOSPHERE : COMPARISON OF THEORY WITH OBSERVATIONS. II. BENESOV BOLIDE SPECTRA

The unique observational spectrum of the very bright Benesov bolide EN 070591 is compared to theoretical bolide spectra. The −19.5 mag bolide was induced by a meteoroid of an estimated initial mass of 4000 kg, a density of 2 g cm−3 and a kinetic energy of1012 J (0.2 kT TNT). The ablating piston model predicts spectra of large bolides by radiative hydrodynamics calculations. We present examples of the calculated H-chondrite vapor spectral opacities and of the resulting spectra for various parameters. Both theoretical and observed spectra show that bolide radiation is composed of atomic line emissions, molecular bands and continuum radiation. The role of the continuum increases with increasing meteoroid size and with decreasing altitude. The atomic lines are produced under the effective excitation temperature of 4000–6000 K. The lines of Fe i are too faint and the lines of Ca i are too bright in the model in comparison with the observations. Also the computed continuum level is too high. These differences can be explained by the fact that the vapors occupy a larger volume and have lower density than predicted. This is probably a consequence of a mutual interaction of fragments after the meteoroid fragmentation and of a not well understood ablation process. Other differences between the theory and the observation are described and possible model improvements are discussed.