Van Allen Belts: May 2024 Solar Storm Breached the Barrier

The "impenetrable barrier" of the Van Allen radiation belts has been breached. According to a study led by physicist Yoshizumi Miyoshi of Nagoya University, published on 28 October 2026 in Geophysical Research Letters, the exceptional solar storm of May 2024 raised the flux of ultra-energetic electrons inside that boundary by more than 5,000 times.

A barrier that was not absolute

Earth's magnetic field traps energetic particles in two doughnut-shaped rings, the Van Allen belts. In 2014, NASA's Van Allen Probes found a surprising boundary about three Earth radii from the planet's center, which the fastest electrons, travelling near the speed of light, almost never crossed. Researchers called it the "impenetrable barrier".

Its origin is still debated. Natural low-frequency radio waves known as plasmaspheric hiss, and possibly human very-low-frequency transmissions, may scatter these electrons toward the atmosphere before they get closer. That is useful, because these "killer electrons" can pass through satellite shielding, damage electronics and shorten spacecraft lifetimes.

In May 2024, a series of solar flares triggered a G5 geomagnetic storm, the maximum on the scale. Japan's Arase satellite, which has monitored the radiation belts since 2017, detected electrons above 3 megaelectronvolts inside the barrier, with a flux more than 5,000 times its pre-storm level.

Not pushed in, but accelerated in place

The data do not show electrons simply being shoved inward. Low-energy electrons rose first, more energetic ones about half a day later, and those above 3 MeV roughly a day after that.

According to the researchers, the storm eroded the plasmasphere, the region of cold plasma around Earth, almost emptying it. That left room for "chorus waves", electromagnetic waves that sound like birdsong when converted to audio, Miyoshi explains. Instead of scattering the electrons, they accelerated them. The plasma took more than four days to refill, versus two normally, so the conditions lasted long enough to produce electrons in large numbers. High levels persisted for months, until the next storm in October 2024.

What it means

There is no risk on the ground: these regions lie more than 10,000 km up, and the atmosphere and magnetic field still protect us. The barrier has not vanished either; it gave way under exceptional conditions, in a storm of a kind seen about once every twenty years. Earlier work in 2018 and 2024 had already questioned the idea of an absolute boundary.

For satellite operators, however, the finding matters. A relatively sheltered zone can see radiation surge during an extreme storm and stay elevated for months. With thousands of satellites launched every year and an active Sun, space weather is a genuine engineering concern.