On shock waves and the role of hyperthermal chemistry in the early diffusion of overdense meteor trains

Abstract

Studies of meteor trails have until now been limited to relatively simple\nmodels, with the trail often being treated as a conducting cylinder, and the\nhead (if considered at all) treated as a ball of ionized gas. In this article,\nwe bring the experience gleaned in other fields to the domain of meteor\nstudies, and adapt this prior knowledge to give a much clearer view of the\nmicroscale physics and chemistry involved in meteor-trail formation, with\nparticular emphasis on the first 100 or so milliseconds of the trail formation.\nWe discuss and examine the combined physico-chemical effects of\nmeteor-generated and ablationally amplified cylindrical shock waves which\nappear in the ambient atmosphere immediately surrounding the meteor train, as\nwell as the associated hyperthermal chemistry on the boundaries of the high\ntemperature postadiabatically expanding meteor train. We demonstrate that the\ncylindrical shock waves produced by overdense meteors are sufficiently strong\nto dissociate molecules in the ambient atmosphere when it is heated to\ntemperatures in the vicinity of 6,000 K, which substantially alters the\nconsiderations of the chemical processes in and around the meteor train. We\ndemonstrate that some ambient O2, along with O2 that comes from the shock\ndissociation of O3, survives the passage of the cylindrical shock wave, and\nthese constituents react thermally with meteor metal ions, thereby subsequently\nremoving electrons from the overdense meteor train boundary through fast,\ntemperature independent, dissociative recombination governed by the second\nDamkohler number. Possible implications for trail diffusion and lifetimes are\ndiscussed.\n