Popular news has several articles linking back to the news article in Nature Earth’s magnetic field is acting up and geologists don’t know why which discusses the need for an early update to the World Geomagnetic Model.
However my question is about one line found in the Independent's Planet’s erratic magnetic field forces emergency update to global navigation system
The shift they observed was so large it was on the verge of exceeding the acceptable limit for navigation errors.
To account for this, scientists at the British Geological Survey and the US National Oceanic and Atmospheric Administration (NOAA) are issuing an unprecedented emergency update to the model.
They have fed in the latest data, including an unexpected geomagnetic pulse that took place beneath South America in 2016, to ensure the system is more accurate.
Question: What is the nature, and underlying cause of the "unexpected geomagnetic pulse that took place beneath South America in 2016"?
AKA geomagnetic jerk.