The South Atlantic Anomaly

Back in the early 1990s, astronauts on NASA's Space Shuttle discovered that their laptops had mysterious crashes when flying above the south Atlantic ocean.

The cause? A phenomenon known as the South Atlantic Anomaly.

Above the Earth's upper atmosphere, energetic charged particles from solar wind get trapped by the Earth and form a vast zone called the Van Allen radiation belt. Any electronic devices exposed to intense radiation from the belt can easily malfunction or crash. To avoid this, orbiting satellites and spacecraft can adjust their altitude and hide underneath the Earth's magnetic field.

But the Earth's magnetic field isn't a smooth spheric shield. Because the Earth's magnetic and rotation axes do not line up perfectly, it causes a part of its magnetic field, located just 200 kilometers (120 miles) above the south Atlantic ocean, is drawn towards the Earth and allows the particles-filled Van Allen belt get closer to the ground, creating the South Atlantic Anomaly.

To cope with the radiation from the anomaly, the International Space Station is equipped with requires extra shielding. The famous Hubble Space Telescope would stop take observations whenever flying through the "dent" in the Earth's magnetic field.

Source: Curious Droid via Youtube