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Meteor-ablated Aluminum in the Mesosphere-Lower Thermosphere
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  • John Maurice Campbell Plane,
  • Shane Daly,
  • Wuhu Feng,
  • Michael Gerding,
  • Juan Carlos Gomez Martin
John Maurice Campbell Plane
University of Leeds

Corresponding Author:[email protected]

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Shane Daly
University of Leeds
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Wuhu Feng
University of Leeds
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Michael Gerding
Leibniz-Institute of Atmospheric Physics
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Juan Carlos Gomez Martin
Instituto de Astrofísica de Andalucía
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Abstract

The first global atmospheric model (WACCM-Al) of meteor-ablated aluminum was constructed from three components: the Whole Atmospheric Community Climate Model (WACCM6); a meteoric input function for Al derived by coupling an astronomical model of dust sources in the solar system with a chemical meteoric ablation model; and a comprehensive set of neutral, ion-molecule and photochemical reactions relevant to the chemistry of Al in the upper atmosphere. The reaction kinetics of two important reactions that control the rate at which Al+ ions are neutralized were first studied using a fast flow tube with pulsed laser ablation of an Al target, yielding k(AlO+ + CO) = (3.7 ± 1.1) × 10-10 and k(AlO+ + O) = (1.7 ± 0.7) × 10-10 cm3 molecule-1 s-1 at 294 K. The first attempt to observe AlO by lidar was made by probing the bandhead of the B2Σ+(v’ = 0) ← X2Σ+(v” = 0) transition at λair = 484.23 nm. An upper limit for AlO of 57 cm-3 was determined, which is consistent with a night-time concentration of ~5 cm-3 estimated from the decay of AlO following rocket-borne grenade releases. WACCM-Al predicts the following: AlO, AlOH and Al+ are the three major species above 80 km; the AlO layer at mid-latitudes peaks at 89 km with a half-width of ~5 km, and a peak density which increases from a night-time minimum of ~10 cm-3 to a daytime maximum of ~60 cm‑3; and that the best opportunity for observing AlO is at high latitudes during equinoctial twilight.
Feb 2021Published in Journal of Geophysical Research: Space Physics volume 126 issue 2. 10.1029/2020JA028792