Please use this identifier to cite or link to this item:
Files in This Item:
File SizeFormat 
Rapp 2009, Charging of mesospheric aerosol particles.pdf566.7 kBAdobe PDFView/Open
Title: Charging of mesospheric aerosol particles: The role of photodetachment and photoionization from meteoric smoke and ice particles
Authors: Rapp, M.
Publishers Version:
Issue Date: 2009
Published in: Annales Geophysicae Vol. 27 (2009), No. 6
Publisher: Göttingen : Copernicus
Abstract: Time constants for photodetachment, photoemission, and electron capture are considered for two classes of mesospheric aerosol particles, i.e., meteor smoke particles (MSPs) and pure water ice particles. Assuming that MSPs consist of metal oxides like Fe2O3 or SiO, we find that during daytime conditions photodetachment by solar photons is up to 4 orders of magnitude faster than electron attachment such that MSPs cannot be negatively charged in the presence of sunlight. Rather, even photoemission can compete with electron capture unless the electron density becomes very large (≫1000 cm-3) such that MSPs should either be positively charged or neutral in the case of large electron densities. For pure water ice particles, however, both photodetachment and photoemission are negligible due to the wavelength characteristics of its absorption cross section and because the flux of solar photons has already dropped significantly at such short wavelengths. This means that water ice particles should normally be negatively charged. Hence, our results can readily explain the repeated observation of the coexistence of positive and negative aerosol particles in the polar summer mesopause, i.e., small MSPs should be positively charged and ice particles should be negatively charged. These results have further important implications for our understanding of the nucleation of mesospheric ice particles as well as for the interpretation of incoherent scatter radar observations of MSPs. © 2009 Author(s).
Keywords: Atmospheric composition and structure (Aerosols and particles; Middle atmosphere composition and chemistry) - Ionosphere (Ion chemistry and composition); aerosol; electron density; ionization; ionosphere; mesosphere; photochemistry
DDC: 550
License: CC BY 3.0 Unported
Link to License:
Appears in Collections:Geowissenschaften

This item is licensed under a Creative Commons License Creative Commons