A Growing Hole in Earth’s Magnetic Field Over the South Atlantic
A weak spot in Earth’s magnetic field, known as the South Atlantic Anomaly, has been expanding steadily for over a decade, troubling scientists monitoring its effects.
Nature of the South Atlantic Anomaly
This anomaly is caused by unusual magnetic behaviors called reverse flux patches. These patches are areas where magnetic field lines reverse direction, plunging back into Earth's core rather than spreading outward. Such behavior is rare and linked to turbulent flows in the molten outer core, which produces the planet’s magnetic field.
Formation and Movement of the Anomaly
The reverse flux patches form where the outer core meets the mantle, creating local weaknesses that allow the anomaly to grow. One of these patches is currently moving westward over Africa, dragging the anomaly with it, as reported by indy100.
Magnetic Field Disruptions and Challenges
Normally, magnetic field lines in the southern hemisphere extend outward from the core. However, inside the anomaly zone, this flow is disrupted, weakening the field inconsistently and complicating efforts to accurately model its changes.
Changes in the Northern Hemisphere Magnetic Field
Simultaneously, magnetic field variations are observed in the northern hemisphere, displaying contrasting trends. Data from the Swarm mission reveals that the magnetic field over Canada has weakened slightly, shrinking by an area roughly the size of India. Conversely, the magnetic influence over Siberia has strengthened, expanding by an area comparable to Greenland.
“Normally, field lines in the southern hemisphere emerge from the core and arc outward. But in the anomaly zone, this flow is disrupted, weakening the magnetic field in a non-uniform way and complicating efforts to model its behavior.”
Data from the Swarm mission show that the magnetic field above Canada has diminished slightly in strength, while the field over Siberia has intensified.
Summary: The South Atlantic Anomaly is a gradually worsening magnetic weakness caused by reverse flux patches in Earth's outer core, while simultaneous, contrasting magnetic changes occur in the northern hemisphere.
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