Lower-Thermosphere Metals and High Altitude Meteoroid Sputtering
Abstract
Recent lidar observations of atomic Fe, Na, and K at altitudes well above the traditional meteor zone violate the usual assumptions regarding atmospheric metals. While suggested sources of these metals include ion-to-neutral conversion and rapid vertical bulk transport due to intense acoustic-gravity wave breaking, we suggest a direct source. That is, confirmation of radar and optical meteors at altitudes well above the ablation-defined meteor zone points to a direct source of these high-altitude metals due to sputtering of cold, fast meteoroids. Interesting complications to this scenario arise as many of these high altitude meteoroids appear to be fragmenting suggesting these are complex "dirty-ice" and "dust-ball" meteoroids comprised of small, dense grains weakly bound together by more volatile substances. As they enter the 150-200 km atmosphere these meteoroids may disperse into a more extended "coma" that presents a more complex interaction region and interaction process with the atmosphere. We discuss sputtering, the impact energies needed for onset of sputtering, sputtering yield, and the observational evidence available for interpretation of meteoroid sputtering as a source of aeronomically interesting metals above the classical meteor zone.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMSA43B2398R
- Keywords:
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- 0355 Thermosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 2419 Ion chemistry and composition;
- IONOSPHEREDE: 2427 Ionosphere/atmosphere interactions;
- IONOSPHEREDE: 2487 Wave propagation;
- IONOSPHERE