On the Influence of Solar Variability on Ion-Mediated Nucleation in the Atmosphere


Authors:  Raffaella D'Auria and Richard P. Turco

Affiliation:  Dept of Atmospheric Sciences, Univ. of California, Los Angeles


In situ formation of new particles in the troposphere is well-documented observationally [e.g., Clarke et al. 1998].  However, a theory that successfully explains the process of particle formation from precursor vapors, is consistent with basic physical and chemical principles, and explains existing data, is still unresolved [e.g., Clarke et al., 1998]. Recently, massive molecular ionic clusters have been detected in the upper troposphere [Eichkorn et al., 2002; Heitmann and Arnold, 1983]. Similar abservations have also been made in the lower troposphere [Eisele, 1988; Tanner and Eisele, 1991], and in the mesosphere. Ionic clusters have the property of stabilizing the formation of condensation nuclei through the strong interaction of a charge center with polar molecules at the atomic scale. Hence, ion production in the atmosphere can influence the abundances of cloud condensation nuclei that ultimately impact Earth's climate. The primary ionization source throughout the lower atmosphere (excluding the first few kilometers over land) are galactic cosmic rays (GCRs). Because the intensity of galactic cosmic radiation penetrating into the middle and lower atmosphere is significantly modulated by solar activity, a potentially critical connection may exist between solar activity and changes in climate forcing as mediated by ionic clusters. In this paper we present results from an ongoing research effort to determine the atmospheric roles of ionic clusters with respect to heterogeneous chemistry and cloud microphysics. In the present talk, we focus on the properties and growth of small molecular clusters that form on hydronium, nitrate and sulfate core ions with water, nitric acid, and sulfuric acid ligands. We present results that describe the sensitivity on cluster properties and behavior to changes in ionization levels and ambient environmental conditions.



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