Studying Ionosphere Using SKA-Low and SKA-Mid
The Earth's ionosphere introduces systematic effects that limit the performance of radio interferometers operating at low frequencies ($\lesssim 1$\,GHz). These ionospheric effects intensify during periods of heightened geomagnetic activity or for observations with extended baseline configurations. As each Pathfinder telescope operates at a different magnetic latitude, they experience distinct ionospheric regimes, offering complementary insights into ionospheric behaviour. In this work, we present a comparative study of ionospheric disturbances using observations from the uGMRT, VLA, MWA, and LOFAR, spanning a wide range of geographic and geomagnetic conditions. We present both antenna-based and field-based analyses to quantify phase fluctuations, positional offsets, and scintillation effects across these arrays. The measured total electron content (TEC) gradients reveal variations in spatial and temporal ionospheric structures with sensitivities that exceed those achievable with Global Navigation Satellite System (GNSS) measurements. By combining multi-telescope results, we assess the impact of ionospheric turbulence on calibration and imaging fidelity, and use these findings to forecast the expected ionospheric effects on observations with SKA-Low and SKA-Mid.