Constraining the luminous efficiency of meteors

Abstract

a b s t r a c tWe propose a new approach for studying the radiation of a fireball, one of the main processes which occur when the meteor body enters the planetary atmosphere. The only quantities which directly follow from the available observations are the fireball brightness, its height above sea level, the length along the trajectory, and as a consequence its velocity as a function of time. Other important parameters like meteoroid's mass, its shape, bulk and grain density, temperature remain unknown. The present study takes recent results in fireball aerodynamics and considers them together with the classical postulate that a fraction of the meteoroid kinetic energy is transformed into radiation during its flight. This gives us a new analytical dependence, which in particular shows that the fireball luminosity in general is proportional to the body pre-entry mass value, its initial velocity to the power of 3, and the sine of the slope between horizon and trajectory. Research helps in finding an answer to the general important question: Which fraction of the fireball kinetic energy is transformed into light during meteoroid drag and ablation in the atmosphere? Ó

Simulation of the capabilities of an orbiter for monitoring the entry of interplanetary matter into the terrestrial atmosphere

“…However, as it requires detailed analysis of each meteor (including light curves and photography) it is not appropriate here. Another method, more easily automated, was recently proposed (Gritsevich, 2009;Gritsevich and Koschny, 2011). This method is entirely based on the interpretation of variations of speed and height as consequences of braking and mass loss (ablation/erosion).…”

“…where μ is a coefficient ranging from 0 to 2/3 and representing the effect of the object's change of shape (related to its rotation, which may distribute heat all around the surface and prevents shape change) (Gritsevich and Koschny, 2011). Eq.…”

“…Three input parameters need to be known: c d A e : Unless the shape of the object is known a priori (exceptional case, e.g., Ayers et al, 1970) or a meteorite can be retrieved and provide some hints on the original pre-atmospheric body (Gritsevich, 2008), it can only be assumed. Example of values found in meteor science are 1.21 for a body with an initial spherical shape, 1.55 as in Halliday et al (1996) or 1.65 used in Verniani (1966) for non perfectly spherical shape, and 1.8 for a brick-like shape (Gritsevich and Koschny, 2011), or c d A e ¼ 1:1 considering a small c d for a spherical body (Wetherill and Revelle, 1981;Revelle and Ceplecha, 2001).…”

“…Further details of the method, justifications and example of applications may be found in (Gritsevich, 2007;Gritsevich and Koschny, 2011). A very useful example of application of this method is proposed in .…”

“…While α, β and estimation of masses had already been obtained (Gritsevich, 2009) for the set of Canadian Network meteors analyzed in Section 3.4, the implementation into SAT allows us to perform the calculations with different assumptions (for mass estimation) and combine them with the latest development of the method: the determination of τ as in Gritsevich and Koschny (2011). The determination of mass and luminous efficiency requires assumption on the density ρ m .…”