Mobility Distributions and Mass Distributions of Atmospheric Ions near the Ground

Abstract

The atmosphere near the ground is weakly ionized by cosmic rays and radioactive substances emanated from the ground. Both positive and negative atmospheric ions are produced and their concentrations are typically of 102 – 10cm3. The primary positive ions, most of which are nitrogen and oxygen molecular ions, rapidly react with ambient neutral species to form stable ions. At the same time, electrons ejected from nitrogen or oxygen molecules immediately attach to ambient molecules to become primary negative ions. Through successive ion-molecular reactions, stable negative ions are formed. At the ground level, atmospheric ions are lost by the ion-ion recombination and by the attachment to aerosol particles. The lifetime of atmospheric ions is approximately several hundreds of seconds in relatively clean atmosphere near the ground surface (Ferguson et al., 1979). Within the lifetime, minor neutral species at concentration of ppt level can be involved in atmospheric ion-molecular reactions. Therefore, the ion composition in the lower troposphere is the most complex through all levels of atmosphere.