A powerful geomagnetic superstorm struck Earth on May 10-11, 2024, compressing the planet's protective plasmasphere to unprecedented levels. Observations from Japan's Arase satellite revealed the outer edge shrinking from 44,000 km to just 9,600 km above the surface. The event, the strongest in over two decades, also triggered rare auroras in equatorial regions and highlighted recovery challenges due to ionospheric disruptions.
The Gannon storm, also called the Mother's Day storm, erupted from major solar eruptions that hurled billions of tons of charged particles toward Earth. Within nine hours of impact, the plasmasphere—a region of charged particles shielding satellites and technology—contracted to about one-fifth its normal size. This marked the most severe compression recorded since the Arase satellite began operations in 2017.
Launched by the Japan Aerospace Exploration Agency in 2016, Arase was ideally positioned to capture plasma waves and magnetic field changes during the event. Ground-based GPS receivers complemented the data, tracking ionospheric variations that supply particles to the plasmasphere. Recovery proved unusually protracted, lasting over four days, due to a 'negative storm' that depleted ionospheric particle levels through atmospheric heating and chemical changes.
"We tracked changes in the plasmasphere using the Arase satellite and used ground-based GPS receivers to monitor the ionosphere," explained Dr. Atsuki Shinbori, lead researcher from Nagoya University's Institute for Space-Earth Environmental Research. "This prolonged disruption can affect GPS accuracy, interfere with satellite operations, and complicate space weather forecasting."
The storm's intensity pushed auroras equatorward, visible in mid-latitude areas like Japan, Mexico, and southern Europe—far from their typical polar confines. Several satellites faced electrical issues, GPS signals degraded, and radio communications faltered as a result. These findings, detailed in a 2025 Earth, Planets and Space study, enhance predictions for future space weather impacts on technology.