Climatological Characteristics of the Polar Ionosphere Based on the Chatanika and Sondrestrom Incoherent Scatter Radars

Since they came into operation in 1960s, incoherent scatter radars have contributed significantly in advancing our understanding of the polar ionosphere, as well as the solar wind-magnetosphere-ionosphere coupling. Enormous amount of data over the polar ionosphere has been accumulated so far and archived in the CEDAR database. Thus, it is timely to examine the climatological characteristics of the polar ionosphere, utilizing such a wealthy database. We are particularly interested in the electric field and ionospheric conductance measurements by the Chatanika and Sondrestrom IS radars, which cover approximately the auroral and polar cap regions, respectively. By combining these two quantities, it is further possible to deduce the overhead ionospheric current distributions. The climatological characteristics thus inferred are compared with various model distributions. As an attempt to evaluate the induction effect of the earth's interior over the two IS radar sites, the ionospheric current density derived from the radar measurement is compared with the corresponding ground magnetic disturbance. Also examined is the effect of the field-aligned current on the ground magnetic disturbance, particularly on the D component.