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Abstract

The height-integrated ionospheric Pedersen conductance is a crucial parameter in estimating ionospheric Joule heating, which in turn has a large impact on the thermospheric chemical composition and circulation during periods of increased geomagnetic activity. As the conductance is difficult to measure directly in extended regions, statistical models and proxies are often used. We estimate the Pedersen conductance using magnetic and electric field data provided by the Swarm satellites. Two assumptions are needed in the analysis. 1) The height-integrated Pedersen current is identical to the curl-free part of the height integrated ionospheric horizontal current. This is not usually valid in individual cases, but it should be a reasonable approximation in a statistical sense. 2) The cross-track magnetic disturbance measured by Swarm is mostly produced by field-aligned currents and not affected by ionospheric electrojets. When both assumptions are satisfied, the height-integrated Pedersen conductance can be directly estimated from the ion velocity and the magnetic perturbation. The result is valid both in the case of quasi-static MI-coupling and idealized Alfven wave reflection at the ionospheric boundary. We present results of a statistical study utilizing 9 years of data from the Swarm-A and Swarm-B satellites. Careful selection and filtering of the data are required, which tends to limit the analysis to regions where the ion velocity and magnetic disturbances are reasonably strong, i.e. close to the auroral ovals. Statistical Pedersen conductance maps are derived for the Northern and Southern auroral regions during different seasons and levels of geomagnetic activity.