Constraints on Meteoric Smoke Composition and Meteoric Influx Using SOFIE Observations With Models

Abstract

The composition of meteoric smoke particles in the mesosphere is constrained using measurements from the Solar Occultation For Ice Experiment (SOFIE) in conjunction with models. Comparing the multiwavelength observations with models suggests smoke compositions of magnetite, wüstite, magnesiowüstite, or iron‐rich olivine. Smoke compositions of pure pyroxene, hematite, iron‐poor olivine, magnesium silicate, and silica are excluded, although this may be because these materials have weak signatures at the SOFIE wavelengths. Information concerning smoke composition allows the SOFIE extinction measurements to be converted to smoke volume density. Comparing the observed volume density with model results for varying meteoric influx (MI) provides constraints on the ablated fraction of incoming meteoric material. The results indicate a global ablated MI of 3.3 ± 1.9 t d−1, which represents only iron, magnesium, and possibly silica, given the smoke compositions indicated here. Considering the optics and iron content of individual smoke compositions gives an ablated Fe influx of 1.8 ± 0.9 t d−1. Finally, the global total meteoric influx (ablated plus surviving) is estimated to be 30 ± 18 t d−1, when considering the present results and a recent description of the speciation of meteoric material.

Response to the reviewers

“…However, one way forward is first to select the wavelength dependence of the real RIs, which have a much smaller impact on the extinction cross section than the imaginary RIs in the absorption-dominated regime. The literature data for haematite from Hsu and Matijevic (1985), Longtin et al (1988), andQuerry (1985) very satisfactorily fit the experimental data across the whole wavelength range within experimental errors using the RDG approximation (Fig. 6, red line).…”

Unravelling the microphysics of polar mesospheric cloud formation

“…MSPs are nanoparticles which form by re-condensation of material ablated from meteoroids entering the upper atmosphere (Plane et al, 2015). Recent studies estimated that about 40 t of cosmic material enters the atmosphere each day (Carrillo-Sánchez et al, 2016;Hervig et al, 2017). Approximately 20 % of this material ablates in the upper atmosphere with the major elemental species being Fe, Mg, and Si (Vondrak et al, 2008).…”

“…Approximately 20 % of this material ablates in the upper atmosphere with the major elemental species being Fe, Mg, and Si (Vondrak et al, 2008). The ablated elemental species then form oxide, hydroxide, and carbonate compounds below 85 km and polymerize into nanometre-sized particles (Plane et al, 2015), which are likely present in the form of magnetite (Fe 3 O 4 ), wüstite (FeO), magnesiowüstite (Mg x Fe 1−x O, x = 0-0.6), or iron-rich olivine (Mg 2x Fe 2−2x SiO 4 , x = 0.4-0.5) (Hervig et al, 2017;Rapp et al, 2012). Strong atmospheric circulation limits the average lifetime of these particles in the summer mesopause such that they only reach sizes below about r = 2 nm (Bardeen et al, 2008;Megner et al, 2008a, b;Plane et al, 2014).…”

Optical properties of meteoric smoke analogues

“…Important progress has also been achieved using remote sensing techniques: the SOFIE (Solar Occultation for Ice Experiment) instrument on the AIM (Aeronomy of Ice in the Mesosphere) satellite has detected MSPs by optical extinction, conducting solar occultation measurements from April 2007 to the present. Extinction measurements at 330, 867 and 1037 nm were used to show that the best-fit particle compositions are iron-rich oxides (magnetite (Fe 3 O 4 ), wüstite (FeO), magnesiowüstite (Mg x Fe 1−x O, x = 0 − 0.6)) or iron-rich olivine (Mg 2x Fe 2−2x SiO 4 , x = 0.4 − 0.5) (Hervig et al, 2017). That is, the major meteoric elements Fe, Mg and Si are either mixed in olivinic particles with a single average composition, or MSPs are a mix of metal oxide and silica particles.…”