On Shock Waves and the Role of Hyperthermal Chemistry in the Early Diffusion of Overdense Meteor Trains

TL;DR

This paper investigates the microscale physics and hyperthermal chemistry involved in meteor trail formation, emphasizing shock wave effects and atmospheric molecule dissociation within the first 100 milliseconds after meteor entry.

Contribution

It introduces a detailed physical and chemical model of overdense meteor shock waves and hyperthermal reactions, advancing understanding beyond simple cylindrical models.

Findings

Shock waves dissociate atmospheric molecules at ~6000 K.

Oxygen molecules survive shock dissociation and react with meteor ions.

Implications for meteor trail diffusion and lifetime are discussed.

Abstract

Studies of meteor trails have until now been limited to relatively simple models, with the trail often being treated as a conducting cylinder, and the head (if considered at all) treated as a ball of ionized gas. In this article, we bring the experience gleaned in other fields to the domain of meteor studies, and adapt this prior knowledge to give a much clearer view of the microscale physics and chemistry involved in meteor-trail formation, with particular emphasis on the first 100 or so milliseconds of the trail formation. We discuss and examine the combined physico-chemical effects of meteor-generated and ablationally amplified cylindrical shock waves which appear in the ambient atmosphere immediately surrounding the meteor train, as well as the associated hyperthermal chemistry on the boundaries of the high temperature postadiabatically expanding meteor train. We demonstrate that the cylindrical shock waves produced by overdense meteors are sufficiently strong to dissociate molecules in the ambient atmosphere when it is heated to temperatures in the vicinity of 6,000 K, which substantially alters the considerations of the chemical processes in and around the meteor train. We demonstrate that some ambient O2, along with O2 that comes from the shock dissociation of O3, survives the passage of the cylindrical shock wave, and these constituents react thermally with meteor metal ions, thereby subsequently removing electrons from the overdense meteor train boundary through fast, temperature independent, dissociative recombination governed by the second Damkohler number. Possible implications for trail diffusion and lifetimes are discussed.