A Comparison of Fireball Luminous Efficiency Models using Acoustic Records

TL;DR

This study combines optical and acoustic measurements to evaluate and compare luminous efficiency models of fireballs, finding good agreement for stony meteors but significant differences for iron meteorites, which could help identify their composition.

Contribution

It validates the Borovička et al. (2020) luminous efficiency model using acoustic data and highlights potential signatures of iron fireballs based on energy disparities.

Findings

Borovička et al. (2020) model agrees within a factor of two for stony fireballs.

Iron fireballs show an order of magnitude higher luminous efficiency than model predictions.

Disparities between optical and acoustic energies may indicate iron meteorite composition.

Abstract

The total energy of a fireball is commonly obtained from optical measurements with an assumed value for luminous efficiency. Acoustic energy measurements offer an independent means of energy estimation. Here we combine optical and acoustic methods to validate the luminous efficiency model of Borovi\v{c}ka et al. (2020). Our goal is to compare these models with acoustic measurements of meteoroid energy deposition. Employing theoretical blast scaling laws following the approach of McFadden et al. (2021), we determine explosive yields for both fireball fragmentation events and cylindrical shocks for four different bright fireballs. We model fireballs using the MetSim software (Vida et al., 2023) and find that the Borovi\v{c}ka et al. (2020) model produces agreement better than a factor of two for our three chondritic fireball case studies. The major exception is an iron meteorite-producing fireball where the luminous efficiency is an order of magnitude higher than model predictions calibrated with stony fireballs. We suggest that large disparities between optical and acoustic energies could be a signature of iron fireballs and hence useful as a discriminant of that population.