Diurnal Variations of the Electric Field in the Atmospheric Boundary Layer

The results of experimental and theoretical studies of diurnal variations in the atmospheric electric field in the surface layer are presented. The gradient of the potential of the atmospheric electric field was measured at the Cheget Peak station (3040 m above sea level) in the high-mountain zone of the Elbrus region, where no significant anthropogenic impact is available and the unitary variation features appear in the diurnal course of the electric field. An analysis of observational data has indicated that the diurnal variation of the electric field has a morning (0200-0400 UT) minimum and daytime (0600-1100 UT) and evening (1600-1900 UT) maxima, the positions of which depend on surface wind speed. Local variations are caused by electric-field perturbations resulting from the space charge at the Earth's surface due to the electrode effect and the influence of turbulent mixing. Analytical solutions of the equation for the total electric current in the region of the electrode effect have been obtained and investigated. In the case of the classical electrode effect, the oscillations of the electric field and current coincide in time, but differ in amplitude, depending on the characteristic scale of the electrode layer. In a turbulent stably stratified surface layer, if the electric field strength on the Earth's surface is constant (i.e., there is no diurnal variation), it has been found that, with an increase in the turbulence coefficient in the diurnal variation of the electric field, the maxima and minima of the diurnal variation shift by 2-3 h relative to current density fluctuations. An increased electric field slightly reduces the shift due to the increased influence of the classic electrode effect, which inhibits the effects of turbulence.