Simulated Trends in Ionosphere‐Thermosphere Climate Due to Predicted Main Magnetic Field Changes From 2015 to 2065

Abstract

The strength and structure of the Earth's magnetic field is gradually changing. During the next 50 years the dipole moment is predicted to decrease by ∼3.5%, with the South Atlantic Anomaly expanding, deepening, and continuing to move westward, while the magnetic dip poles move northwestward. We used simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model to study how predicted changes in the magnetic field will affect the climate of the thermosphere-ionosphere system from 2015 to 2065. The global mean neutral density in the thermosphere is expected to increase slightly, by up to 1% on average or up to 2% during geomagnetically disturbed conditions (K p ≥ 4). This is due to an increase in Joule heating power, mainly in the Southern Hemisphere. Global mean changes in total electron content (TEC) range from −3% to +4%, depending on season and UT. However, regional changes can be much larger, up to about ±35% in the region of ∼45 • S to 45 • N and 110 • W to 0 • W during daytime. Changes in the vertical ⃗ E × ⃗ B drift are the most important driver of changes in TEC, although other plasma transport processes also play a role. A reduction in the low-latitude upward ⃗ E × ⃗ B drift weakens the equatorial ionization anomaly in the longitude sector of ∼105-60 • W, manifesting itself as a local increase in electron density over Jicamarca (12.0 • S, 76.9 • W). The predicted increase in neutral density associated with main magnetic field changes is very small compared to observed trends and other trend drivers, but the predicted changes in TEC could make a significant contribution to observationally detectable trends.

Non-monotonic growth and motion of the South Atlantic Anomaly

“…where φ and θ are longitude and co-latitude, respectively. Similar planetary-scale averages were recently invoked to quantify the Pacific/Atlantic geomagnetic SV dichotomy (Dumberry and More 2020) or the northern/southern differences in the SV-induced neutral density of the thermosphere (Cnossen and Maute 2020). Note that while the choice of the mid-term year 1930 in the denominator of (3) is completely arbitrary, this has no consequence on the resulting rate of change of the SAA area.…”

Analysis and Attribution of Climate Change in the Upper Atmosphere From 1950 to 2015 Simulated by WACCM‐X

“…Changes in the Earth's magnetic field produce changes in the ionosphere that are very location dependent, with the strongest effects occurring in the region of ∼50–50°N and ∼100°W to 50°E (Cnossen & Richmond, 2008, 2013; Cnossen, 2014). Effects of changes in the Earth's magnetic field on thermosphere temperature are strongest at high magnetic latitudes (Cnossen, 2014; Cnossen et al, 2016; Cnossen & Maute, 2020), although exact patterns differed between different studies. The main way in which the magnetic field can affect the thermosphere temperature is via changes in Joule heating.…”

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

“…The cooling trend has been confirmed by observations, notably by thermosphere density derived from satellite drag (e.g., Emmert et al., 2004; Keating et al., 2000) and ion temperature in the F2‐region derived from incoherent scatter radars (e.g., Ogawa et al., 2014; Zhang et al., 2016). However, finding trend in ionospheric parameters such as the height of the maximum electron density of the F2 region (hmF2) and the peak electron density (NmF2) has proved to be more challenging, due to their high sensitivity also to many other drivers like the solar and geomagnetic activity (GA), Earth’s magnetic field, stratospheric ozone, atmospheric dynamics (see, e.g., Cnossen & Maute, 2020; Laštovička, 2013; Laštovička et al., 2012; Qian et al., 2011, and references therein). The extraction of CO 2 ‐driven trend requires careful removal of effects from all other drivers, which can cause potential errors and uncertainties in the derived trend as comprehensively summarized in Laštovička and Jelínek (2019).…”