Technique: large-scale ionospheric conductance estimated from combined satellite and ground-based electromagnetic data

A technique for estimating the large-scale spatial distribution of the height-integrated electrical conductivity (conductance) of the Earth's high-latitude ionosphere is presented. By combining satellite magnetic perturbation data with ground-based magnetometer and HF radar observations the Hall (ΣH) and Pedersen (ΣP) conductances are independently calculated. Magnetic perturbations observed at the Earth's surface are combined with those recorded by satellites to calculate the horizontal ionospheric current (J⊥). Combined HF radar and satellite ion drift data give the ionospheric electric field (E⊥ ), which combined with J ⊥ allows ΣH and ΣP to be estimated from Ohm's law. Conductance results from preliminary application of the technique to an event with a 1 hour integration time are presented. Significant uncertainties arise due to sparse ground magnetometer and electric field coverage. The resulting conductance distribution shows an enhancement in the auroral regions as expected from a statistical model conductance. However, the calculated conductance enhancement is located between the region 1 and region 2 Birkeland currents. This agrees with the statistical model data in the morning sector but disagrees in the evening sector. Comparison of the conductance results with conductance data inferred from in situ precipitating particle observations shows colocated enhancements. The calculated data also show a low (<1) Hall to Pedersen conductance ratio in regions near downward Birkeland current.