A note on the altitude profiles of the electron production in the atmosphere by micrometeoroids entering it at different initial speeds

摘要

We have extended our earlier model (Mendis et al., 2005) for the study of the dynamical, thermal and charging history of micrometeoroids entering the earth's atmosphere, by taking into account the role of sputtering, which is important for high-speed ones. As before we confine ourselves to motion in the night side of the earth.. In this short note we will not discuss these, but will confine our attention to the limited, yet important, effect of electron production in the atmosphere, by three different classes of micrometeoroids (fast—"cometary," average—"cometary," and slow—"asteroidal"). It is seen that the altitude profiles of the electron production, which lead tithe radar signatures of these bodies, are different, not just quan tilitatively but also qualitatively. This is due to the different relative importance of the three processes responsible for electron production, namely the ones associated with ablation and sputtering of the infalling micrometeoroid and thermionic electrqn emission from it. It is seen that sputtering-associated electron production is the dominant process, particularly at higher altitudes, for the fast micrometeoroid (initial entry speed 60 km/s), ablation-associated electron production is the dominant process for the average one (initial entry speed 30 km/s), while thermionic electron emission is the dominant process for the slow one (initial entry speed 12.5 km/s).