# Perpendicular Electrical Conductivity in the Topside Ionosphere Derived from Swarm Measurements
## 4 Discussion
Althoughperpendicular conductivities have been obtained through observed plasma parameters (in situ electron density and temperature) and the collision frequencies between charged and neutral particles have been neglected in the derivation of corresponding formulas, the coupling with the neutral atmosphere is implicit in the plasma parameters' variations. Indeed, neutral density acts as a background for the electron density (and drives the vertical distribution of the ionic and molecular species), and the same is true for the neutral temperature which is a lower limit for the electron temperature. During high solar activity, increased Extreme Ultra Violet (EUV) radiation enhances ionisation, leading to higher electron densities and stronger equatorial ionisation anomalies. This enhancement is more significant for the Pedersen conductivity, which directly impacts the vertical plasma drifts [121]. The Hall conductivity also increases, influencing the lateral spread of the ionisation peaks. Seasonal changes impact the EIA due to variations in solar zenith angle and thermospheric winds, which modulate the distribution and intensity of ionisation by affecting both conductivities. In summary, the roles of Hall and Pedersen conductivities are fundamental in understanding, for example, the behaviour of the EIA at Swarm altitudes. Their influence on plasma drifts and ionisation distribution highlights the complex interplay between solar activity, seasonal variations, and ionospheric conductivities, shaping the equatorial ionisation anomaly [122; 123]. While the features reconstructed using direct measurements from the Swarm constellation align well with theoretical expectations, it is essential to acknowledge the limitations and uncertainties inherent to the study. The spatial and temporal variability of ionospheric parameters, such as local fluctuations in electron density and temperature, can introduce uncertainties in conductivity measurements. The omission of minor ion species, which can significantly affect conductivity values, may lead to the underestimation or overestimation of actual conductivities, especially under varying ionospheric conditions. Additionally, the ionosphere-thermosphere system is influenced by various factors, including neutral winds, pressure gradients, and magnetic field variations, leading to complex interactions and feedback mechanisms that are challenging to model accurately. For example, while our study shows a clear relationship between increased EUV flux and enhanced ionisation, the actual response of the ionosphere can vary significantly depending on other concurrent factors. Moreover, our approximations assume a certain degree of homogeneity and stability in the ionospheric environment, which may not always hold true. Real-world ionospheric conditions are subject to rapid changes and localised disturbances, potentially leading to deviations from average descriptions. Therefore, while our study provides valuable insights into the roles of Hall and Pedersen conductivities in shaping the EIA, it is crucial to interpret these findings within the broader context of ongoing research. At high latitudes, the ionospheric conductivities and associated currents are influenced by different processes. The auroral electrojet currents and FACs are prominent features. The Pedersen conductivity at high latitudes can be significantly enhanced by particle precipitation and auroral activity, leading to strong horizontal currents. The Hall conductivity, which is also affected by particle precipitation, contributes to the perpendicular current systems but generally has a lower magnitude compared to the Pedersen conductivity. The dependence on solar activity and seasonal changes is evident here as well, with increased solar activity leading to enhanced auroral activity and corresponding increases in both Hall and Pedersen conductivities.