Long-Term Trends of Ionospheric Day-to-Day Variability During the Past Century

In this study, we explore the long-term trend of ionospheric day-to-day variability induced by atmospheric perturbations over the past century, using time-slice simulations by the whole atmospheric model. The main results show that the magnitude of the trends in the past century maximizes ∼±1% of the seasonal mean per decade. Analysis of the contributing factors reveals that geomagnetic secular variation primarily contributes to the trends over the American-Atlantic sector, while increasing greenhouse gases (GHG) explain most trend patterns over the Asia-Pacific region. Additional evidence by Wuhan ionosonde observations covering the period of 1947–2024, supports the simulated negative trend, and the magnitude agrees well with the simulations. Furthermore, our analysis of atmospheric tides revealed that the weakening of SE2 day-to-day variability due to increasing GHG levels is a plausible cause. Our findings thus indicate that ionospheric weather-like variability also undergoes long-term trends significantly under the climate change scenario.