Ions in the Terrestrial Atmosphere and Other Solar System Atmospheres

Abstract

Charged molecular clusters, traditionally called small ions, carry electric currents in atmospheres. Charged airborne particles, or aerosol ions, play an important role in generation and evolution of atmospheric aerosols. Growth of ions depends on the trace gas content, which is highly variable in the time and space. Even at sub-ppb concentrations, electrically active organic compounds (e.g. pyridine derivatives) can affect the ion composition and size. The size and mobility are closely related, although the form of the relationship varies depending on the critical diameter, which, at 273 K, is about 1.6 nm. For ions smaller than this the separation of quantum levels exceeds the average thermal energy, allowing use of a molecular aggregate model for the size-mobility relation. For larger ions the size-mobility relation approaches the Stokes-Cunningham-Millikan law. The lifetime of a cluster ion in the terrestrial lower atmosphere is about one minute, determined by the balance between ion production rate, ion-ion recombination, and ion-aerosol attachment.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

“…Theoretical formulations for recombination and attachment coefficients exist (e.g. Harrison and Tammet 2008;, and the electron detachment rate can be found from thermodynamic considerations.…”

Electrical Charging of Volcanic Plumes

“…However, whatever the initial charge distribution, subsequent scavenging processes will inevitably modify the charge distribution and are very likely to produce polarity differences as a function of particle size. The impact of ion and aerosol scavenging (Harrison and Tammet 2008) on electric charge distribution in volcanic plumes has not yet been systematically explored, but a basic thermodynamic approach has been illustrated by Mather and Harrison (2006). Some atmospheric potential gradient (PG) data recorded during eruptions have shown rapid step-like changes that have been attributed to lightning discharges.…”

Composition and Measurement of Charged Atmospheric Clusters

“…Near the surface, polar organic species act as ligands producing a wide variety of clusters, depending on trace gas concentrations (Elrod 2003;Parts and Luts 2004). Pyridine (an organic heterocyclic molecule with formula C 5 H 5 N) is a particularly efficient, and therefore common, ligand for positive cluster ions because of its high proton affinity (Elrod 2003), even though it only exists in tiny atmospheric concentrations (Harrison and Tammet 2008). Negative ion species are dominated by relatively simple nitrate and sulphate-based clusters, but some organic core species e.g.…”

“…On the molecular scale, they attach and recombine to form neutral complexes (Klemperer and Vaida 2006). The detailed physics of atmospheric ions and their interaction with aerosol particles is discussed in companion papers by Harrison and Tammet (2008) and Tripathi et al (2008).…”