Analysis and modeling of the GLO-1 observations of meteoric metals in the thermosphere

Abstract

The GLO-1 experiment measured the radiance of ambient atmospheric species and of meteoric metals, including Na, Mg, Mg + and Ca +, along lines of sight with tangent altitudes between 120–350 km. The results confirm earlier observations of a strong dawn/dusk asymmetry in thermospheric ion density and the concentration of ion density near the geomagnetic equator. The data also show a substantial amount of neutral Na in the thermosphere, with a dawn/dusk asymmetry similar to the ions. We observe the presence of Ca + and Mg + in the relative abundance comparable to the abundance ratio in meteoric material and in the sun. We are also able to simultaneously observe Mg and Mg + in a few cases, over a range of altitudes. We have developed a model in an attempt to better understand these features. The one–dimensional model realistically and comprehensively incorporates the deposition of cosmic dust, transport by the equatorial electric field and diffusion, and ion and neutral chemistry specific to the three metal species studied. The model is driven by a single source function for dust influx, so that it can be used to predict the relative amounts of one metal species to another. These features of the model allow for diurnal variations and variations in latitude, reproducing the observations reasonably well on average.