Simulated trends in ionosphere-thermosphere climate due to predicted main magnetic field changes from 2015 to 2065

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Friday, May 15, 2020

Summary or Abstract: The strength and structure of the Earth's magnetic field is gradually changing. These changes do not only affect the difference between the geographic and magnetic pole, which we have to consider when we hike in higher latitude regions. The upper atmosphere also reacts to these changes, since the plasma distribution in the upper atmosphere is strongly influenced by Earth's magnetic field, and can feed back to the neutral atmosphere through ion-neutral coupling. With our increasing number of space assets and reliance an them, it is important to understand the space environment changes the Earth's magnetic field will introduce. In this study will we use a predictive model of the Earth's magnetic field together with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model to provide some guidance about the expected upper atmosphere changes from 2015 and year 2065. In general, during the next 50 years the dipole moment is predicted to decrease, with the South Atlantic Anomaly expanding, deepening, and continuing to move westward, while the magnetic dip poles move north-westward. 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 (Kp >= 4). These density trends are small compared to other trend drivers. 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 ~45deg S-45deg N and 110deg W-0 deg W during daytime. Changes in the vertical ExB 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 ExB drift weakens the equatorial ionization anomaly in the longitude sector of ~105deg W-60deg W, manifesting itself as a local increase in electron density over Jicamarca (12.0deg S, 76.9deg W). The predicted changes in TEC could make a signifcant contribution to observationally detectable trends.

Photograph of TEC in 2015
TEC [TECU] in 2015 (left) and the difference between 2065 and 2015 (right) at 18 UT averaged over all days of the year. The black triangle marks the location of Jicamarca.

 

Publication Name: JGR Space Physics
First HAO Author's Name: Astrid Maute

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