HR: 0800h
AN: SA21A-0273    [Abstracts]
TI: The importance of charging processes for mesospheric ice nucleation
AU: * Gumbel, J
EM: gumbel@misu.su.se
AF: Stockholm University, Department of Meteorology, Stockholm, 11140, Sweden
AU: Megner, L
EM: linda@misu.su.se
AF: Stockholm University, Department of Meteorology, Stockholm, 11140, Sweden
AU: Rapp, M
EM: rapp@iap-kborn.de
AF: Leibniz Institute for Atmospheric Physics, Schlossstrasse 6, Kühlungsborn, 18225, Germany
AB: Meteoric smoke particles are considered the most likely condensation nuclei for ice in the mesosphere. Open nucleation questions concern the number and size distribution of smoke. The critical radius above which neutral smoke can act as condensation nuclei is about 1 nm. Hence, while the smoke population is thought to be dominated by sub-nanometer particles, only larger particles are considered important for ice nucleation. Recent model simulations show that the global circulation efficiently transports meteoric material away from the summer pole, resulting in a shortage of condensation nuclei just at the summer mesopause. This provides a challenge for our current understanding of NLC and PMSE. In this paper we argue that smoke charging is critical for the nucleation of mesospheric ice. As the Gibbs free energy barrier disappears for charged particles at sufficiently low temperatures, charging can remove the 1 nm size threshold of ice nucleation. We show that this is feasible at typical mesospheric temperatures and, hence, that all charged smoke regardless particle size can be turned into condensation nuclei. This in turn has large implications for the number and size distribution of NLC and PMSE ice particles. Of central importance is the question what fraction of meteoric smoke is actually charged. We discuss this in terms of microscopic smoke properties and the charging processes prevailing in the D-region dusty plasma.
DE: 0340 Middle atmosphere: composition and chemistry
DE: 2423 Ionization processes (7823)
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2461 Plasma interactions with dust and aerosols (7849)
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting