Electrical properties of fog

Abstract

The electrical properties of fog are described in detail on the basis of full-scale aeroelectrical observations and theoretical estimations. The measured electric field and spectrum of its pulsation are given in line with the simultaneous amplitude-time records of the vertical components of electric current and electric field. Fog located near the observation site is shown to decrease the density of current and generally changes its sign. As a rule, variation of the density of current shows a coil-like behavior, which means that it smoothly (over several hours) approaches the region where the current changes the direction and relatively sharply goes back to the stationary state of the unperturbed atmosphere near the ground. Fog is shown to increase the intensity of electric field pulsation by more than an order of magnitude. Nevertheless, in the majority of observations, the exponent of the spectrum does not differ drastically from the exponent of the spectrum for the conditions of good weather. Structure-time and spectral analyses of electric-field pulsation are carried out. The results of structure-time analysis offer the possibility of specifying two types of electrical states of fog: one is characterized by aeroelectric structures and another, by chaotic structure-time variations. The system of basic equations describing fog in the approximation of quasi-electrodynamics is formulated. The effect of fog-particle properties and air-ionization characteristics on the diffusion charging of particles is estimated numerically. Stationary vertical profiles of the charge of fog particles, electric field, charge density, and light-ion concentration are studied theoretically. Possible mechanisms of formation of the electric-field spectra are discussed and their relationships with the spectra of electric charge density are discussed with allowance for neutral gas turbulence and aeroelectric structures in fog.