Abstract This study investigates the ionospheric saturation effect in the total electron content (TEC) response to solar activity using long-term global ionospheric map data spanning 1999–2024. Empirical mode decomposition is used to isolate long-term solar-cycle variability, and a two-segment regression model provides a consistent diagnostic of the saturation threshold in TEC versus solar proxy F10.7p. The global distribution exhibits pronounced local-time and seasonal patterns, with strong occ