# Perpendicular Electrical Conductivity in the Topside Ionosphere Derived from Swarm Measurements
## 4 Discussion
This model is freely usable online and provides the height profile of conductivities, height-integrated values (i.e., conductances), and maps for specific days and LT or UT hours. The model implements the conductivity equations from Maeda [105] with the collision frequencies in Banks and Kockarts [116] and uses the outcomes of the International Reference Ionosphere (IRI) model by [PERSON] et al. [114] and the atmospheric model by [PERSON] [117]. By running the WDC model to retrieve conductivity height profiles, for example, for the date 21 June 2018 (at the June solstice and at a fairly central point in the time window used in this work) at the location 15\({}^{\circ}\) of geographic latitude, 0\({}^{\circ}\) of geographic longitude, between 400 and 500 km of altitude and at noon UT (corresponding to a QD magnetic latitude of 4.2\({}^{\circ}\) and 11.8 MLT), we find \(\sigma_{||}\sim 10^{11}\) s\({}^{-1}\) and \(\sigma_{P}\sim 10^{4}\) s\({}^{-1}\) (the \(\sigma_{H}\) profile is not provided by the WDC model in the selected range of altitudes), which is consistent with our results (see Figures 1 and 5). Proceeding in the same way, we checked that the results obtained in our study (particularly for the dependence of conductivities on seasons) are consistent with those provided by the WDC model. We, however, note that this comparison is made to the best of our capabilities, as the WDC model provides (1) local vertical conductivity profiles (at fixed geographic longitude and latitude and LT); (2) conductance maps (at a fixed geographic longitude and latitude and LT or UT). Neither of these provides maps that are directly comparable with our conductivity maps, so we can only limit ourselves to a fairly approximate comparison based on orders of magnitude. The dependence of conductivities on solar activity and seasons allows the indirect investigation of the distinct electrical structures and physical processes they are associated with. For instance, at Swarm altitude, where the reconstructed distributions of the conductivities are referenced, we can observe the EIA and the FACs, both of which are influenced by the anisotropic conductivities of the ionosphere. Looking at the equatorial region in the F-region at Swarm altitude, the EIA is still relevant but is more spread out. The vertical plasma drifts caused by the daytime eastward electric field and the Earth's magnetic field (\(\mathbf{E}\times\mathbf{B}\) motion) create peaks in electron density at about \(\pm 15^{\circ}\) QD magnetic latitude. These plasma drifts are significantly influenced by the Hall and Pedersen conductivities, which play a crucial role in modulating the structure and behaviour of the EIA, in conjunction with zonal and meridional neutral winds. At low latitudes, the Pedersen conductivity facilitates the vertical movement of plasma. At the equator, plasma is vertically lifted by \(\mathbf{E}\times\mathbf{B}\) and then diffuses along the geomagnetic field lines toward higher latitudes under the influence of gravity and pressure gradient forces, thus leading to the formation of the EIA's characteristic crests. During periods of high solar activity, the increased solar flux enhances the electron density, which in turn leads to enhanced Pedersen and Hall conductivities, resulting in more pronounced equatorial ionisation anomalies. Seasonal changes impact both the Hall and Pedersen conductivities through variations in both the charged and neutral components of the ionosphere-thermosphere system. Indeed, the neutral density, collision frequencies, and thermospheric winds also show specific patterns exhibiting seasonal variations. These seasonal variations can alter both the effectiveness of the plasma drifts and the resulting ionisation distribution. For instance, at low latitudes, perpendicular conductivities exhibit annual and semiannual anomalies (Figures 5 and 6) that affect not only the ionospheric plasma but also the neutral atmosphere at those altitudes, as demonstrated by satellite observations and models [118; 119; 120].