Non-monotonic growth and motion of the South Atlantic Anomaly

The South Atlantic Anomaly (SAA) is a region at Earth's surface where the intensity of the magnetic field is particularly low. Accurate characterization of the SAA is important for both fundamental understanding of core dynamics and the geodynamo as well as societal issues such as the erosion of instruments at surface observatories and onboard spacecrafts. Here, we propose new measures to better characterize the SAA area and center, accounting for surface intensity changes outside the SAA region and shape anisotropy. Applying our characterization to a geomagnetic field model covering the historical era, we find that the SAA area and center are more time dependent, including episodes of steady area, eastward drift and rapid southward drift. We interpret these special events in terms of the secular variation of relevant large-scale geomagnetic flux patches on the core-mantle boundary. Our characterization may be used as a constraint on Earth-like numerical dynamo models.

Automated summary

The South Atlantic Anomaly (SAA) is a region on Earth's surface with a particularly low intensity of the magnetic field. Accurate characterization of the SAA is crucial for understanding core dynamics, geodynamo, and addressing societal issues. Research indicates that the SAA area and center exhibit time dependency, including periods of stability, eastward drift, and rapid southward drift.