Ion Densities and Particle Charges for Alpha Ionization in an Aerosol Atmosphere: Columnar Recombination Corrections

Ionization by alpha sources in an environment containing small aerosol particles is of interest in aerosol neutralizes, particle chargers and atmospheric electricity. It is known that the conventional ion-balance equation is inadequate in describing the bulk ion densities for alpha sources in view of the columnar recombination process. An earlier self-consistent formulation to include this effect is extended to the case of unequal ionic mobilities and the consequent asymmetric charging of particles. Calculations for medium (Radon-222) and low (Thorium-232) energy sources commonly encountered indicate that the columnar recombination corrections lower the ion densities and the particle mean charges by a factor of about 2 for weak sources (strength < 10³ ions cm^?3 s^?1) and by a factor of 1.2 for strong sources (strength = 10⁹ ions cm^?3 s^?1). The paper presents a detailed study of the dependence of the correction factors as a function of particle concentration and the strength of the alpha sources.