The effect of local irregularities on large-scale ionospheric currents

Abstract

Measurements performed by the low-altitude satellites MAGSAT and TRIAD have discovered small-scale (L ⊥<80 km) magnetic fluctuations at high latitudes. A relation between the fluctuation intensity, ionospheric conductivity and Birkeland currents was also revealed. We assume that the magnetic perturbations are caused by small-scale ionospheric irregularities. We discuss here the influence of random ionospheric irregularities on the effective conductivity. Through analytical consideration, it is concluded that the Pedersen effective conductivity may noticeably deviate from the average conductivity. The effect depends primarily on conditions of Hall current closing. Wherever the Hall currents flow is impossible for any reason, the influence of weak irregularities is negligible. Zones of the equatorial and polar electrojets with electric field directed along electrojets are examples. Analytical consideration conducted for the regions exterior to these zones has shown that random weak ionospheric irregularities double the total Pedersen effective integral conductivity increases. It is usually suggested in the description of the ionospheric conductivity that the ionosphere is either homogeneous or exhibits local irregularity. The background sporadic irregularities in the ionosphere usually small scale is also well known. The research concentrated on two main items: the contribution of a random wind and conductivity field to the background and magnetospheric quasi-stationary electric and magnetic field, and the influence of small stochastic ionospheric irregularities on the effective ionospheric conductivity.