Simulated Long-Term Evolution of the Ionosphere During the Holocene

To date, no natural media is available to derive the ancient ionosphere, so the current understanding of ionospheric long-term trends mainly comes from analyzing similar to 70 yr modern measurements supplemented by theoretical simulations. In this study, for the first time, we expanded the ionosphere simulation to the whole Holocene (9455 BCE to 2015 CE) using the Global Coupled Ionosphere-Thermosphere-Electrodynamics Model developed at the Institute of Geology and Geophysics, Chinese Academy of Sciences, driven by a realistic geomagnetic field, CO2 level, and solar activity, all of which are a combination of ancient media derivations and modern observations. Through a series of control runs, we found that the ionospheric oscillation of the global mean profile is characterized by a nonlinear variation versus geomagnetic field effect, a decrease (increase) above (below) similar to 200 km due to CO2 increase, and violent oscillations in phase with changes in solar activity, with corresponding contributions of approximately 20%, 20%, and 60%, respectively. The CO2 effect became nonnegligible and even more significant after similar to 1800 CE. The solar activity effect is marked by a frequently occurring grand solar minimum. The ionospheric characteristics show linear variations versus the dipole moment of the geomagnetic field, the CO2 level, and the F10.7 index, with the growth rate having significant local time and latitude variations. Our prediction shows that a 400 ppm CO2 increase will cause a global mean decrease of 1.2 MHz in foF2, 34 km in hmF2, and 4 tecu in TEC, which will directly influence radio wave communication.

Automated summary

Currently, there is no natural media available to study the ancient ionosphere, so the understanding of long-term trends mainly comes from analyzing modern measurements and theoretical simulations. In this study, the ionosphere simulation was expanded to the whole Holocene, driven by a combination of ancient media derivations and modern observations. It was found that the ionospheric oscillation is influenced by the geomagnetic field, CO2 levels, and solar activity. The CO2 effect became more significant after 1800 CE, and the solar activity effect is marked by grand solar minimums.