# Perpendicular Electrical Conductivity in the Topside Ionosphere Derived from Swarm Measurements
## 3 Results
### Seasonal Variation of Electrical Conductivity Perpendicular to the Geomagnetic Field
\begin{table}
\begin{tabular}{c c c c c c} \hline  & **Minimum Value** & **Maximum Value** & **Minimum Uncertainty (\%)** & **Maximum Uncertainty (\%)** & **Maximum Conditioned Uncertainty (\%)** \\ \hline December solstice & 4.6 & \(1.2\times 10^{6}\) & 0.7 & 59.4 & 4.7 \\ June solstice & 0.1 & \(4.3\times 10^{5}\) & 0.7 & 70.7 & 5.2 \\ March equinox & 15.4 & \(1.9\times 10^{6}\) & 0.8 & 70.7.5 & 4.9 \\ September equinox & 19.9 & \(1.1\times 10^{6}\) & 0.4 & 70.7 & 4.9 \\ \hline \end{tabular}
\end{table} 
Table 2: Seasonal values of \(\sigma_{P}\). Figure 5: Seasonal maps in QD-MLT coordinates of Pedersen electrical conductivity, \(\sigma_{P}\), around (from top to bottom) the December solstice, the June solstice, the March equinox, and the September equinox. Seasons were selected as specified in the text. Values within each bin are saturated above 10\({}^{6}\) s\({}^{-1}\) and below 10\({}^{2}\) s\({}^{-1}\). Figure 6: _Cont._  
Figures 5 and 6 show features that are strongly dependent on the geomagnetic latitude. At low latitudes, the high \(\sigma_{P}\) and \(\sigma_{H}\) values, associated with the EIA, are maximised at the March equinox, and the values at the December solstice are sensibly higher than at the June solstice, irrespective of the hemisphere. In other words, perpendicular conductivity shows both the semiannual and the annual anomalies as those characterising the F-layer electron density [95; 96; 97; 98; 99; 100]. The semiannual anomaly is associated with the observation that \(Nm\)F2 values at equinoxes are larger than at solstices. \(Nm\)F2 is the electron density associated with the F2 layer, i.e., the maximum electron density in the ionosphere. [PERSON] et al. [101] conducted a detailed study showing how the amplitudes of the semiannual anomaly depend on solar activity, seasons, and the local time. They highlighted that (1) the amplitudes are larger for years of maximum solar activity than for years of minimum solar activity; (2) the amplitudes are larger in the middle and low latitudes than in the high latitudes; (3) there is a tendency of having larger amplitudes around the March equinox than around the September equinox, especially for daytime during low solar activity years. Figures 5 and 6 are climatological seasonal maps based on magnetic and plasma data going from April 2014 to 31 March 2022 and then including periods of both high and low solar activity. Both figures show larger values of conductivity for the March equinox, and this might also be due to a greater weight of low solar activity values when calculating the mean as the value representative of each bin. The annual anomaly is associated with the observation that \(Nm\)F2 values at the December solstice are significantly greater than those at June solstice, globally. This further demonstrates how much perpendicular conductivities are tied to the underlying electron density variations. Differently, mid and high latitudes show a marked seasonal variation. There is an increase in perpendicular conductivity during the local summer compared to the local winter. In fact, around the December solstice, features of \(\sigma_{P}\) and \(\sigma_{H}\) are enhanced in strength and extension in the Southern Hemisphere with respect to the Northern Hemisphere, while around the June solstice, these features are enhanced in the Northern Hemisphere with respect to the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Minimum Value** & **Maximum Value** & **Minimum** & **Maximum** & **Maximum** \\  & **(s\({}^{-1}\))** & **(s\({}^{-1}\))** & **Uncertainty (\%)** & **Uncertainty (\%)** & **Conditioned** \\  & & & & & **Uncertainty (\%)** \\ \hline December solstice & 0.0 & \(3.1\times 10^{4}\) & 1.0 & 66.7 & 5.1 \\ June solstice & 0.0 & \(5.5\times 10^{3}\) & 1.0 & 70.7 & 5.9 \\ March equinox & 0.0 & \(6.5\times 10^{4}\) & 1.0 & 70.7 & 5.1 \\ September equinoxes & 0.0 & \(3.0\times 10^{4}\) & 1.0 & 70.7 & 5.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Seasonal values of \(\sigma_{H}\).