Ionospheric conductance due to electron and ion precipitations based on the comparison between EISCAT and DMSP estimates

Energetic particle precipitation is the major source of electron production that controls the ionospheric Pedersen and Hall conductances at high latitudes. Typically, the ionospheric conductances are estimated using either theoretical or empirical equations. The former method requires several ionospheric and thermospheric parameters as inputs. By contrast, empirical equations are simple, such as Robinson formulas and Galand formulas that have been widely used. In this study, we evaluate the empirical formulas of ionospheric conductances during four different types of auroral precipitation conditions based on 63 conjugate events observed by DMSP and EISCAT. The conductances calculated from the DMSP data with the empirical formulas are compared with those based on EISCAT measurements with the standard equations. The best correlation between these two is found when the empirical Robinson formulas are used in the presence of diffuse electron precipitation without ions. In the presence of ion precipitation, the correlation coefficients are smaller, but the correlation improves when the Galand formulas are used to estimate the contribution of ion precipitation to the conductances. For the condition of pure ion precipitation, the ionospheric conductances are increased up to 2-7 S for Pedersen and 2.5-10 S for Hall conductances. The increase is larger for a higher geomagnetic AE index. Overall, the empirical formulas applied to the DMSP particle spectra underestimate the ionospheric conductances.