Evolution and Disappearance of the paleo-West Pacific Anomaly: implications to the South Atlantic Anomaly

Paleomagnetism and modern geomagnetic measurements indicate that SAA is undergoing rapid changes, with rapid expansion of area and rapid decreasing of intensity. Even in recent years SAA has expanded the minor minima seen in southern Africa. This has led to speculation that the expanding SAA may be an indicator of an upcoming geomagnetic reversal. However, how to know the future evolution direction of SAA is still debatable.

Apparently, the study of the changes of other SAA-like structure anomaly regions in history has important implications for the study of SAA evolution. Here, we focus on the evolution and disappearance of the paleo West Pacific Anomaly (WPA). Utilizing the gufm1 model, it is found that WPA occurred between 1620 and 1810 CE. Over its duration, WPA underwent phases of rapid expansion, drift, and split, eventually the primary part vanished, while a new segment persisted and expanded. The striking similarity in evolutionary behavior between WPA and the rapid expansion, drift, and recent splitting in the SAA over the past century is noteworthy. This similarity can be attributed to the fact that WPA, like the SAA, is controlled by the reversal flux patch in the CMB on the northern hemisphere. Therefore, we posit WPA as a significant magnetic anomaly in the Northern Hemisphere, and propose that its evolutionary patterns can serve as predictive indicators for the future evolution of the SAA. Studying the evolution of WPA is an important means to understand the global magnetic field and the evolution of Southeast Asia magnetic field. It is of great significance for us to understand the nature of SAA and predict the evolution trend of SAA.