Perturbation of Ozone by Enhancements in Meteoric Smoke Following Major Meteor Showers

Between 5 – 300 tons of meteoric material is deposited in the Earth’s atmosphere each
day. The uncertainty in that estimate is large due to limitations in the different instrumental and analytical techniques used to obtain meteoric mass fluxes — and the fact that no single technique can provide an integrated estimate over the entire size distribution. Recent estimates of mass fluxes seem to be biased toward the lower quarter of this quantity (e.g., 40 — 50 tons per day) — and this estimate contains both contributions from meteorite and cosmic dust infall.  In the case of cometary dust, the average velocity of an incoming meteorite is less than 15 km/s (though greater than 11 km /s — Earth’s escape velocity), and some 20% of the infalling mass is converted to meteoric smoke (nanometer-scale metallic particles of meteoric origin) via ablative processes (whose efficiency increases as a function of velocity). This accounts for roughly 10 tons meteoric smoke per day.

These particles subsequently sediment toward the poles during their 4-year lifetime, serving as mesospheric and stratospheric cloud nuclei and possibly participating directly in ozone chemistry.

 

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Meteor showers are periodic events that occur when the Earth’s orbit sweeps past the path of a cometary debris trail and can present orders-of-magnitude enhancements in the daily meteoric flux rate over zonally localized regions. This morning I woke up to see a paper on correlations between large meteor showers and changes in total ozone: Gorbanev et al. (2017) explore TOMS measurements over several decades, using autocorrelation techniques. The decreases they find are significant — on the order of 5 DU. Figure 1, below, demonstrates the autocorrelation peaks of total ozone with the radar-returned meteor infall rate.

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Figure 1: The autocorrelation functions from the total
ozone measured during annual meteor showers as a function of Time lag (days). (From Gorbanev et al. [2017])

The authors then demonstrate the disruption of the seasonal Autumnal enhancement in northern hemispheric ozone by the occurrence of the Leonid showers (figure 2, below). Following peak meteor activity, total ozone declines by about 5 DU over a period of 14 days (November 18 — December 2). Following the disturbance, total ozone resumes its seasonal trend.

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Figure 2: 1999 northern hemispheric total ozone.  The Leonid meteor shower disrupts the seasonal increase in ozone by about 5 DU over a period of two weeks. The seasonal trend recovers and resumes afterward. (From Gorbanev et al. [2017])

The authors conclude that this signal can be used to identify interactions between meteoric material and the atmosphere. Their story is open access and available at this link.

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