Earth's "impenetrable" radiation shield has been breached for the first time.

 Earth's "impenetrable" radiation shield has been breached for the first time.

Earth is wrapped in belts of radiation, and part of them was thought to have an impenetrable barrier. But a huge solar storm in May 2024 seems to have broken through it.

Earth's magnetic field traps charged particles from the Sun in two donut shaped zones called the Van Allen belts.

Some of these particles are extremely fast electrons, sometimes called killer electrons, because they can damage satellites and harm astronauts.

In 2014, NASA's Van Allen Probes found a sharp inner edge, about three Earth radii from the planet's center, that the most energetic electrons almost never crossed. It was nicknamed the impenetrable barrier.

In May 2024, powerful eruptions from the Sun caused the strongest geomagnetic storm in about two decades.

Researchers led by Yoshizumi Miyoshi at Nagoya University in Japan studied data from Japan's Arase satellite.

After the storm, the number of very high energy electrons inside the barrier jumped more than 5,000 times compared with before.

Lower energy electrons rose first, and the most energetic about a day later.

The researchers say this pattern suggests the electrons were not simply pushed inward. Instead, they were likely sped up right there, inside the barrier.

The storm drained away cold gas near Earth, allowing natural radio waves called chorus waves to boost the electrons' energy.

"Here we show that this barrier can be breached under extreme space weather conditions," the researchers wrote.

The extra electrons slowly faded over several months.

There are caveats. The findings come from one storm seen by one satellite, so it is unclear how often this happens.

The acceleration was inferred from the data, not measured directly.

Understanding this could help protect satellites and astronauts in future storms.

RESEARCH PAPER

Yoshizumi Miyoshi et al., "Local Acceleration of Multi-MeV Electrons Inside Earth's Impenetrable Barrier During the May 2024 Superstorm," Geophysical Research Letters (2026).