A perspective on the luminous efficiency approach for meteoroid mass estimation

Abstract

A perspective on the luminous efficiency approach for determining the pre-atmospheric mass of a meteoroid from a measured light-curve is presented for meteors in the continuum flow regime. This perspective interprets the mass-loss rate evaluated from the luminous efficiency approach as a solution to the meteoroid surface energy balance, with the measured light-curve serving as a proxy for the radiative heating to the meteoroid surface. This differs from the standard interpretation that equates the radiation from the light-curve to a change in the kinetic energy of the meteor. Mathematically, the developed perspective is identical to the standard luminous efficiency approach, except that the deceleration term is shown to be extraneous. This perspective provides a clear relationship between the measured light-curve and the mass loss of a meteor, which is based on the observation that the radiative heating that drives the mass loss (through the surface energy balance) also provides the radiation for the light-curve. Furthermore, this perspective provides a simple mathematical framework for interpreting the impact of fragmentation on the luminous efficiency. This framework shows that the luminous efficiency of a fragmented meteoroid is a weighted sum of the luminous efficiency from the various fragments, which may each be assessed based on single-body simulations. To generate these single-body simulations, state-of-the-art flowfield and radiation simulations are performed for meteoroid diameters ranging from 0.02 to 100 m, velocities ranging from 12 to 24 km/s, and altitudes ranging from 20 to 50 km. The luminous efficiency values resulting from these simulations are distilled into a correlation and applied to trajectories resulting from the fragment cloud method. This allows the integral luminous efficiency to be computed using the developed luminous efficiency model and defined fragmentation framework. Both the silicon and visible passbands are considered. For the silicon passband, the computed integral luminous efficiency values track closely with the experimentally derived integral luminous efficiency model developed by Brown et al. (2002). This represents the first theoretical derivation of the integral luminous efficiency approach based on fully coupled radiation and ablation simulations with viscous effects, which also captures the impact of individual meteoroids that are combined using the developed fragmentation framework.