Collaborative Research: Experimental Investigation of Micrometeoroid Ablation

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In this project, a laboratory a study aimed at measuring the evaporation rate and ionization efficiency of particles representing interplanetary dust particles will be combined with models to interpret radar measurements of meteor head echoes in the Earth's atmosphere, which are generated by ablation. Much of the laboratory work, which utilizes a dust accelerator facility at the U. of Colorado, is being funded by NASA. The NSF project will focus on interpreting meteor radar measurements performed at sites including Poker Flat, AK, Arecibo, PR, Jicamarca, Peru, and radars in Argentina, Japan and Norway. NSF will support the coordination between the laboratory results, modeling, and radar data interpretation, as well as undergraduate student participation in the laboratory measurements.Layers of neutral metal atoms, such as Fe, Mg, Ca, K and Na, which peak between 85 and 95 km and are ~20 km in width, are produced by the daily ablation of Interplanetary Dust Particles. Once the meteoric metals are injected into the Earth's upper atmosphere they are responsible for a range of phenomena in addition to the formation of layers of metal atoms and ions, such as nucleation of noctilucent clouds; impacts on stratospheric aerosols and ozone chemistry; and fertilization of the ocean with bio-available iron. Current estimates for the total mass of the micrometeoroid input that is ablated in the upper atmosphere vary by two orders of magnitude. The accurate determination of the total incoming mass is relevant to determining vertical transport in the middle atmosphere and to the surface, and our understanding of dust evolution in the solar system. Radar detection of micrometeors is a widely used technique to constrain the mass input. The laboratory work undertaken by the U. of Colorado will provide much improved measurements of the key parameter needed to interpret these measurements: the ionization efficiency during the ablation process upon atmospheric entry.