South Atlantic Anomaly as marker of geomagnetic jerks during satellite era

Abstract

The South Atlantic Anomaly (SAA) is an area with values of the geomagnetic field intensity lower than expected ones. The SAA represents one of the most important features of the present geomagnetic field and it is related to the presence of reversed flux patches at the Core-Mantle Boundary. In the satellite era, it has been observed that the SAA areal extent has been continuously growing, with periods alternating positive and negative accelerations. Periods with minima in the acceleration of the SAA areal extent seem to be related to the occurrences of geomagnetic jerks for the last 2 decades. This finding was published in 2021 using the CHAOS-7.2 model. Here, we use the new updated CHAOS-7.16 release to confirm these results, especially relevant in very recent times when edge effects could have affected previous calculations. This new analysis reinforces the proposed link and weaken the idea of a connection by chance. We have also analyzed the acceleration of the areal extent of South American and African reversed flux patches at the Core-Mantle Boundary related to the presence of the SAA at surface and have registered minima in the same periods when they are observed in the SAA at surface. As geomagnetic jerks are sudden changes in the geomagnetic field secular variation related to changes in outer core flow patterns, this result could reinforce the hypothesis that the core dynamics involved in the origin of jerks is related to the physical processes that produce the reversed flux patches, and in turn the SAA evolution.