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Title: The ECOMA 2007 campaign: Rocket observations and numerical modelling of aerosol particle charging and plasma depletion in a PMSE/NLC layer
Authors: Brattli, A.Lie-Svendsen, Ø.Svenes, K.Hoppe, U.-P.Strelnikova, I.Rapp, M.Latteck, R.Torkar, K.Gumbel, J.Megner, L.Baumgarten, G.
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Issue Date: 2009
Published in: Annales Geophysicae, Volume 27, Issue 2, Page 781-796
Publisher: München : European Geopyhsical Union
Abstract: The ECOMA series of rocket payloads use a set of aerosol particle, plasma, and optical instruments to study the properties of aerosol particles and their interaction with the ambient plasma environment in the polar mesopause region. In August 2007 the ECOMA-3 payload was launched into a region with Polar Mesosphere Summer Echoes (PMSE) and noctilucent clouds (NLC). An electron depletion was detected in a broad region between 83 and 88 km, coincident with enhanced density of negatively charged aerosol particles. We also find evidence for positive ion depletion in the same region. Charge neutrality requires that a population of positively charged particles smaller than 2 nm and with a density of at least 2×108 m−3 must also have been present in the layer, undetected by the instruments. A numerical model for the charging of aerosol particles and their interaction with the ambient plasma is used to analyse the results, showing that high aerosol particle densities are required in order to explain the observed ion density depletion. The model also shows that a very high photoionisation rate is required for the particles smaller than 2 nm to become positively charged, indicating that these may have a lower work function than pure water ice.
Keywords: Aerosols and particles; Atmospheric composition and structure; Composition and chemistry; Ion chemistry of the atmosphere; Middle atmosphere; aerosol; atmospheric chemistry; atmospheric structure; density; mesopause; middle atmosphere; numerical model; plasma
DDC: 530
License: CC BY 3.0 Unported
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