Geomagnetic Shield Weakening Over North America, Claim Chinese Researchers

Over the last 30 years, the magnetic field strength in the region has dropped to a level that is barely above the global average.

Chinese scientists have claimed that the magnetic shield over North America is weakening rapidly while strengthening in the eastern hemisphere. Led by Professor Fang Hanxian of the National University of Defence Technology, the study, published in Review of Geophysics and Planetary Physics, claims the shift of the geomagnetic poles from the western to the eastern hemisphere might be the possible reason for the "exceptionally fast" loss of the field strength. Fang's team used the latest models and data to reconstruct the global magnetic field strength change since 1900.

The findings showed that between 1930 to 1990, the field strength in North America increased and was higher than in many other regions of the world. However, over the last three decades, especially by 2020, the magnetic field strength in the region had dropped to a level that is barely above the global average.

"After 2000, the speed exceeded 50km per year, far surpassing the movement speed of the magnetic pole in the southern hemisphere," Fang was quoted as saying by SCMP.

"Apart from the weakening magnetic field in North America, the strength in other major regions is showing an increasing trend," Fang said, adding that Australia, the North Atlantic Ocean and Africa were experiencing the fastest growth.

Over the past century, the magnetic pole in the northern hemisphere had drifted eastward at a speed of about 10 km per year, the study highlighted.

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The geomagnetic shield

Earth's geomagnetic field, also called the magnetosphere, is a kind of natural barrier that protects the planet from harmful cosmic radiation which can cause erosion of our atmosphere by solar winds. Unlike planets in our immediate vicinity such as Mercury, Venus and Mars, Earth is surrounded by powerful, dynamic forces that play the role of gatekeeper, repelling unwanted energy and trapping most of it at a safe distance from the planet in a twin doughnut-shaped zones called the Van Allen Belts.

In 2018, a study by the National Autonomous University of Mexico found that low geomagnetic fields prevailed in the Maya area, just before the Mayan civilisation collapsed. Some other studies have also attributed the downfall of ancient civilisations in Iran and Syria to the sudden changes in the magnetic field.