Geomagnetic Activity Effects on CO₂‐Driven Trend in the Thermosphere and Ionosphere: Ideal Model Experiments With GAIA

Abstract

We examine impacts of geomagnetic activity (GA) on CO2‐driven trend in the ionosphere and thermosphere using the Ground‐to‐topside Atmosphere Ionosphere model for Aeronomy whole atmosphere model. The model reveals three salient features. (1) Geomagnetic activities usually weakens the CO2‐driven trend at a fixed altitude. Among the IT parameters analyzed, the thermosphere mass density is the most robust indicator for CO2 cooling effect even with GA influences. (2) Geomagnetic activities can either strengthen or weaken the CO2‐driven trend in hmF2 and NmF2, depending on local time and latitudes. This renders the widely used linear fitting methods invalid for removing geomagnetic effects from observations. (3) An interdependency exists between the efficiency of CO2 forcing and geomagnetic forcing, with the former enhances at lower GA level, while the latter enhances at higher CO2 concentration. This could imply that the CO2‐driven trend would accelerate in periods of declining GA, while magnetic storms may have larger space weather impacts in the future with increasing CO2. These findings provide a preliminary model framework to understand interactions between the CO2 forcing from below and the geomagnetic forcing from above.

Mechanisms for Zonal Mean Wind Responses in the Thermosphere to Doubled CO2 Concentration

“…Between 20° and 60 𝐴𝐴 • S above ∼220 km altitude, the ion density decreased by 50% at maximum. These responses of the ion density are consistent with previous model studies and observations (Danilov & Konstantinova, 2013;Laštovička et al, 2008;H. Liu et al, 2021;Ogawa et al, 2014;Qian et al, 2009;Zhang & Holt, 2011).…”

“…The z-coordinate (height) is preferred over the pressure coordinate for ionosphere/thermosphere studies not only because it facilitates comparison with observations (mostly made at certain heights), but also because the ionosphere and the ion drag (the most important factor in the upper atmosphere) are better organized with height. Many studies on the long-term trend in the ionosphere/thermosphere have been carried out in z-coordinate, for example, Keating et al (2000), Emmert, Picone, et al (2004), Emmert, Fejer, et al (2004, Marcos et al (2005), Saunders et al (2011), Solomon et al (2015, Cnossen (2020), H. Liu et al (2020), and H.-L. Liu et al (2021).…”

Impact of Anthropogenic Emission Changes on the Occurrence of Equatorial Plasma Bubbles

“…We set a constant solar minimum condition in this work, but how the EPB occurrence changes with increasing anthropogenic emissions under different solar conditions still needs investigation. In addition, as H. Liu et al (2021) reported, geomagnetic activity could strengthen or weaken CO2-driven climate change in the upper atmosphere. The ionospheric long-term trend is also influenced by geomagnetic activity (Mikhailov & Marin, 2000; S. R. Zhang & Holt, 2013).…”

Response of atmospheric carbon dioxide to the secular variation of weakening geomagnetic field in whole atmosphere simulations

“…Considering the CO 2 variability, Cnossen (2020) analyzed the long-term database of WACCM-X using a modified regression method to examine the impact of CO 2 and geomagnetic field changes on upper atmosphere climate change. Based on a whole atmosphere model, GAIA, the CO 2 doubling effect in the upper atmosphere and the dependence of geomagnetic activity upon the CO 2 -driven trend have been investigated recently (Liu HX et al, 2020, 2021. Nonetheless, to our knowledge, the interaction between CO 2 change and geomagnetic field variation has not been investigated before.…”