A Giant Hole Is Tearing Through Earth’s Magnetic Field

A Giant Hole Is Tearing Through Earth’s Magnetic Field — And It’s Getting Worse

An expanding weak spot in Earth’s magnetic field has been growing steadily for over a decade above the South Atlantic Ocean, alarming scientists. This region, known as the South Atlantic Anomaly, is caused by unusual magnetic behaviors called reverse flux patches.

What Are Reverse Flux Patches?

Reverse flux patches are areas where magnetic field lines behave unexpectedly by diving back into Earth’s core instead of extending outward. This reversal is uncommon and is thought to arise from turbulent flows in Earth’s molten outer core, which is responsible for generating the planet’s magnetic field.

Causes and Effects of the Anomaly

These anomalies occur where the outer core meets the mantle.
They create local zones of magnetic weakening that contribute to the anomaly's expansion.
One flux patch is drifting westward over Africa, dragging the anomaly along.

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 irregularly and complicating modeling efforts.

Magnetic Field Changes Beyond the Anomaly

The anomaly’s changes are not isolated to the southern hemisphere. In the north, magnetic field trends differ:

Above Canada, the magnetic field strength has decreased slightly.
Over Siberia, the magnetic field has grown stronger.
The strong-field area over Canada has shrunk by a size comparable to India, while Siberia’s region expanded roughly the size of Greenland.

These dynamic magnetic shifts highlight the complexity of Earth’s inner structures and their influence on our planet’s protective shield.

Author’s summary: A growing weak spot in Earth’s magnetic field above the South Atlantic reveals complex core dynamics and shifts, with contrasting changes occurring simultaneously in the northern hemisphere.

Indian Defence Review — 2025-11-11