A chemical model of meteoric ablation
By T. Vondráḱ, J. Plane, S. Broadley, D. Janches. 2008
249 citations recorded by the source corpus.
Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD) is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K) through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides), and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca + in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si) have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K) does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s −1 ) and smallest (10 −17 –10 −13 g) meteoroids, but makes a minor contribution to the overall ablation rate.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/f1344ee45279bdfa279a3f934e8273a36d47f118
How researchers see this paper
The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.
In Astronomy and Astrophysics
Citations in the corpus
- Morphology of sporadic E layer retrieved from COSMIC GPS radio occultation measurements: Wind shear theory examination (2014, methodology): “The meteoric input function, which describes the injection of Fe as a function of height, latitude, and day, is determined from an astronomical model coupled to a chemical meteoric ablation model [Vondrak et al., 2008].”