Two-station television observations of Perseid meteors

The predictions of the dustball meteor ablation theory of Hawkes & Jones have been tested using data from two-station television observations of meteors made during the 1977 and 1978 displays of the Perseid meteor shower. The meteor velocities and the heights at which each meteor began and ended, together with the heights of maximum brightness, were determined for 39 Perseid meteors in the magnitude range M_v = + 4 to – 2. The beginning heights (h_B) were found to be independent of meteor magnitude; they ranged from 105 to 115 km, with a mean value of h_B = 110 ± 1 km. The end heights (h_E) and the heights of maximum brightness (h_M) were independent of meteor magnitude only up to a critical magnitude M_v = 0 (corresponding to a meteoroid of critical mass $$\sim 2\times{10}^{-4}$$ kg). Their mean values were $${h}_\text{E}= 99 \pm 1\,\text{km}\,\text{and}\,{h}_\text{M} = 103 \pm 1$$ km respectively. For meteors brighter than $${M}_\text{v} = 0,\,{h}_\text{E}\,\text{and}\,{h}_\text{M}$$ were, on average, significantly lower than these mean levels, in good qualitative agreement with dust ball theory. By assuming that, at the critical mass, dustball meteoroids disintegrate into their constituent grains just before ablation starts, we find that $$3 - 9\times{10}^{5}\,\text{J}\,\text{kg}^{-1}$$ is require to disintegrate Perseid dust ball material. This value is several times lower than the value adopted by Hawkes & Jones $$1 - 6\times{10}^{6}\,\text{J}\,\text{kg}^{-1}$$, suggesting that Perseid material is weaker than the material considered in the theory of dustball ablation.