The Effects of Thermal Radiation, Conduction and Metoriod Heat Capacity on Meteoric Ablation

Abstract

The classical theory of meteoric ablation is generalized to include the effects of thermal radiation, thermal conduction and heat capacity of the impinging meteoroid, which is assumed to be a solid stony particle. In the magnitude range +3 < M < +10 which embraces the bulk of radio meteors, it is shown that thermal radiation may be neglected but that the onset of ablation is delayed due to the finite heat capacity of the meteoroids. This results in evaporation profiles significantly shorter than predicted by the classical theory. Particles of radius greater than 0.1 cm ( M < +3) develop a marked radial thermal gradient and the stresses due to this thermal shock are sufficient to cause fracture before ablation commences. The smallest fragments will be the first to ablate and the theory predicts that for fragments smaller than 0.01 cm radius, this will occur at an atmospheric density ρ_a = 9 × 10 ⁹υ⁻³ where υ is the meteoric velocity. This is in close agreement with the experimental result of Jacchia et al . (1965) for photographic meteors observed with the Harvard Baker-Super-Schmidt cameras.