Simulated Long‐Term Evolution of the Ionosphere During the Holocene

Abstract

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 ∼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) ∼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 ∼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.

Climate Change in the Thermosphere and Ionosphere From the Early Twentieth Century to Early Twenty‐First Century Simulated by the Whole Atmosphere Community Climate Model—eXtended

“…(2023) and Yue et al. (2022) found that a larger vertical drift in the equatorial region because of decreased geomagnetic fields will result in less electron density around the equator and more in the EIA region which would explain the low latitude electron density changes in Figure 6. Zhang et al.…”

“…A closer look at Figures 6d and 6h leads us to conclude that this is reasonable since there are latitudes where the electron column density increases in the period leading up to 1950. Zhou et al (2023) and Yue et al (2022) found that a larger vertical drift in the equatorial region because of decreased geomagnetic fields will result in less electron density around the equator and more in the EIA region which would explain the low latitude electron density changes in Figure 6. Zhang et al (2011) analyzed nearly four decades of incoherent scatter radar observations and found at noontime a change in electron density of +0.45%/decade at 150 km and between −0.05% and −0.35%/decade at higher altitudes.…”

“…(2023) and Yue et al. (2022) found this difference between the northern and southern hemispheres to be related to the larger movement of the magnetic pole in the north relative to the south, inducing a hemispherical asymmetric change in Joule heating rates.…”

“…Again, this is the case in the southern hemisphere for only the 1970s onward but for the entire ten-decade period in the northern hemisphere. Zhou et al (2023) and Yue et al (2022) found this difference between the northern and southern hemispheres to be related to the larger movement of the magnetic pole in the north relative to the south, inducing a hemispherical asymmetric change in Joule heating rates.…”