Long Term Global Ionospheric Total Electron Content Trend Analysis

Abstract

Simulations based on physical models of the thermosphere-ionosphere system suggest that the ionosphere will sink as the thermosphere cools and contracts in response to increasing greenhouse gas concentrations. As a consequence, long-term trends can be expected in ionospheric parameters such as: total electron content (TEC), the critical frequency of the F2 layer, foF2, and its peak height, hmF2. Since early 1990s, foF2 and hmF2, though to a lesser extent, have been widely analyzed to find these trends. This study shows long-term TEC trends for the period 1999–2023 from available global International GNSS service TEC maps. Using F30, F10.7 or MgII as proxies to filter out the effect of solar EUV, the trends are negative, not only for the mean global value but also for most regions with very few exceptions. This would align with the greenhouse effect hypothesis, even though our results show higher negative trend values than expected theoretically.