The composition of meteoric smoke and the smoke content of mesospheric ice from SOFIE observations

Abstract

This work provides the first observational constraints concerning the composition of meteoric smoke particles (MSP) using measurements from the Solar Occultation For Ice Experiment (SOFIE). Multi-wavelength smoke observations in the polar mesosphere suggest MSP compositions of olivine (Mg 2 x Fe 2−2 x SiO 4, x=0.4 or 0.5), carbon (C), magnetite (Fe 3O 4), wüstite (FeO), or magnesiowüstite (Mg x Fe 1− x O, x=0.1, 0.2, 0.6). The observations exclude smoke compositions of hematite, fayalite, proxene, magnesium silicate, and silica. SOFIE observations further indicate that ice particles comprising polar mesospheric clouds (PMC) contain small amounts of meteoric smoke (0.02–4% by volume). The PMC observations are consistent with smoke compositions of carbon, wüstite, or magnesiowüstite ( x=0.1–0.3). Smoke volume densities determined from MSP observations during Southern polar spring are lower than model results, while smoke volume densities consistent with PMC observations are higher than model results. These differences may be related to the models using a climatological atmosphere since dynamics are a dominant control on MSP abundance. Compared to assuming pure ice, SOFIE retrievals considering ice–smoke mixtures yield smaller ice radii (30%) and higher concentrations (190%).