Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 3 6 2003 10.5194/acpd-3-6721-2003 http://www.atmos-chem-phys-discuss.net/3/6721/2003/ http://www.atmos-chem-phys-discuss.net/3/6721/2003/acpd-3-6721-2003.html http://www.atmos-chem-phys-discuss.net/3/6721/2003/acpd-3-6721-2003.pdf 6721 6732 2003-12-18 Evaporation of high speed sporadic meteors E. Murad C. Roth Air Force Research Laboratory, Space Vehicles Directorate, Hanscom AFB, MA 01731, USA Radex, Inc., 3 Preston Court, Bedford, MA 01730, USA Recent measurements conducted at the Arecibo Observatory report high-speed sporadic meteors having velocities near 50 km/s. The results seem to indicate a bimodal velocity distribution in the sporadic meteors (maxima at ~20 km/s and ~50 km/s). The particles have a maximum mass of ~1 μg. This paper will present an analysis of the ablation of 1 μg meteoroids having velocities of 20, 30, 50, and 70 km/s. The calculations show that there is fractionation even for the fast meteoroids, the effect being particularly noticeable for the 1 μg sporadic particles, and less so for the heavier particles. The relevance of the calculations to the radar observations of the sporadic meteors will be discussed.