# Perpendicular Electrical Conductivity in the Topside Ionosphere Derived from Swarm Measurements
## 3 Results
### Seasonal Variation of Electrical Conductivity Perpendicular to the Geomagnetic Field
Figure 6: Seasonal maps in QD-MLT coordinates the Hall electrical conductivity, \(\sigma_{H}\), 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 \(10^{4}\) s\({}^{-1}\) and below \(10^{-2}\) s\({}^{-1}\). Southern Hemisphere. This is particularly evident at high QD magnetic latitudes, where the hemispheric asymmetry in conductivity values exceeds an order of magnitude. At high latitudes, local seasons take into account the fact that, at the December solstice, it is winter in the Northern Hemisphere and summer in the Southern Hemisphere; at the June solstice, it is summer in the Northern Hemisphere and Winter in the Southern Hemisphere; at the March equinox, it is spring in the Northern Hemisphere and Autumn in the Southern Hemisphere; while at the September equinox, it is Autumn in the Northern Hemisphere and spring in the Southern Hemisphere. In light of this, the seasonal maps of \(\sigma_{P}\) (Figure 7) and \(\sigma_{H}\) (Figure 8) show considerable variation and a significant hemispheric asymmetry. This variability prevents the direct comparison of \(\sigma_{P}\) and \(\sigma_{H}\) maps using the same level of saturation for different seasons. In the Northern Hemisphere, during winter, \(\sigma_{P}\) ranges from 4.6 s\({}^{-1}\) to 2.1 \(\times\) 10\({}^{3}\) s\({}^{-1}\), with a mean value of 224.1 s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.0 s\({}^{-1}\) to 1.9 s\({}^{-1}\), with a mean value of 0.1 s\({}^{-1}\). During summer, \(\sigma_{P}\) ranges from 533.1 s\({}^{-1}\) to 4.0 \(\times\) 10\({}^{3}\) s\({}^{-1}\) with a mean value of 1.2 \(\times\) 10\({}^{3}\) s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.2 s\({}^{-1}\) to 4.6 s\({}^{-1}\) with a mean value of 0.7 s\({}^{-1}\). During spring, \(\sigma_{P}\) ranges from 15.4 s\({}^{-1}\) to 3.5 \(\times\) 10\({}^{3}\) s\({}^{-1}\) with a mean value of 737.4 s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.0 s\({}^{-1}\) to 2.9 s\({}^{-1}\) with a mean value of 0.3 s\({}^{-1}\). During autumn, \(\sigma_{P}\) ranges from 20.8 s\({}^{-1}\) to 2.3 \(\times\) 10\({}^{3}\) s\({}^{-1}\) with a mean value of 749.2 s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.0 s\({}^{-1}\) to 1.6 s\({}^{-1}\) with a mean value of 0.4 s\({}^{-1}\). Thus, in the Northern Hemisphere, during summer, the mean values of \(\sigma_{P}\) and \(\sigma_{H}\) are at least five times higher than in winter and about twice higher than during spring and autumn. The same substantial variations are observed in the Southern Hemisphere. In the Southern Hemisphere, during winter, \(\sigma_{P}\) ranges from 0.1 s\({}^{-1}\) to 7.4 \(\times\) 10\({}^{3}\) s\({}^{-1}\) with a mean value of 71.6 s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.0 s\({}^{-1}\) to 15.5 s\({}^{-1}\) with a mean value of still around 0.0 s\({}^{-1}\). During summer, \(\sigma_{P}\) ranges from 464.7 s\({}^{-1}\) to 1.2 \(\times\) 10\({}^{4}\) s\({}^{-1}\) with a mean value of 1.7 \(\times\) 10\({}^{3}\) s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.1 s\({}^{-1}\) to 22.7 s\({}^{-1}\) with a mean value of 1.0 s\({}^{-1}\). During spring, \(\sigma_{P}\) ranges from 30.9 s\({}^{-1}\) to 9.4 \(\times\) 10\({}^{3}\) s\({}^{-1}\) with a mean value of 566.1 s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.0 s\({}^{-1}\) to 22.1 s\({}^{-1}\) with a mean value of 0.2 s\({}^{-1}\). During autumn, \(\sigma_{P}\) ranges from 23.5 s\({}^{-1}\) to 2.6 \(\times\) 10\({}^{4}\) s\({}^{-1}\) with a mean value of 744.6 s\({}^{-1}\), while \(\sigma_{H}\) ranges from 0.0 s\({}^{-1}\) to 75.4 s\({}^{-1}\) with a mean value of 0.4 s\({}^{-1}\). Thus, in the Southern Hemisphere during summer, the mean values of \(\sigma_{P}\) and \(\sigma_{H}\) are up to an order of magnitude higher than those measured during winter and about five times higher than that during spring and autumn.