The May 10, 2024 Gannon superstorm compressed Earth’s plasmasphere from about 27,340 miles to roughly 5,965 miles within nine hours and took about four days to recover. JAXA’s Arase satellite and ground GPS receivers recorded the rapid collapse and slow refill. Researchers identified a rare negative storm — heating-driven changes in upper-atmosphere chemistry that reduced ionospheric particles and slowed replenishment. These observations clarify how extreme geomagnetic storms prolong disruption to GPS, satellites and space-weather forecasting.
Gannon Superstorm Shrunk Earth’s Plasmasphere to One-Fifth in Nine Hours; Recovery Took Four Days
The May 10, 2024 Gannon superstorm compressed Earth’s plasmasphere from about 27,340 miles to roughly 5,965 miles within nine hours and took about four days to recover. JAXA’s Arase satellite and ground GPS receivers recorded the rapid collapse and slow refill. Researchers identified a rare negative storm — heating-driven changes in upper-atmosphere chemistry that reduced ionospheric particles and slowed replenishment. These observations clarify how extreme geomagnetic storms prolong disruption to GPS, satellites and space-weather forecasting.
12:04 AM, 11/21/2025Science
On May 10, 2024, Earth was struck by its most intense geomagnetic disturbance in more than two decades. The Gannon, or Mother’s Day, superstorm compressed the planet’s plasmasphere — a protective region of ionized particles that helps shield satellites and ground systems from harmful space radiation — to roughly one-fifth of its normal radial extent within about nine hours. Full recovery required nearly four days.
Researchers monitoring the event used data from the Japanese satellite Arase (launched by JAXA in 2016) together with ground-based GPS receivers to track how the plasmasphere and ionosphere responded. Arase travels to an apogee near 19,950 miles, placing it inside the plasmasphere and providing an ideal vantage point for measuring rapid changes in plasma density and magnetic activity.
Under typical conditions, the plasmasphere’s outer boundary extends to roughly 27,340 miles above Earth. During Gannon, measurements showed that boundary collapsed to about 5,965 miles — approximately one-fifth of the usual radius — before gradually refilling. The observation provides a clear, time-resolved picture of how an extreme geomagnetic event can rapidly erode near-Earth plasma environments.
How the storm slowed recovery
Study authors, including Professor Atsuki Shinbori of Nagoya University’s Institute for Space–Earth Environmental Research, found that the storm first caused intense heating near polar regions. That heating triggered a rare phenomenon known as a negative storm, in which atmospheric chemistry changes drive a widespread decrease in ionospheric particle densities rather than the increases typically seen after weaker storms.
“We tracked changes in the plasmasphere using the Arase satellite and used ground-based GPS receivers to monitor the ionosphere — the source of charged particles that refill the plasmasphere,” Professor Shinbori said. “Both layers showed us how dramatically the plasmasphere contracted and why recovery took so long.”
In a negative storm, elevated heating alters chemical reactions in the upper atmosphere, reducing oxygen ions that are normally part of the chain producing hydrogen ions. Those hydrogen ions help replenish the plasmasphere; when they are depleted, the plasmasphere’s recharge is slowed, prolonging disruption to GPS accuracy, satellite operations and space-weather forecasting.
Implications
Documenting this link between negative storms and delayed plasmasphere recovery helps scientists build better models of space-weather impacts and predict how long infrastructure may remain vulnerable after extreme events. Improved understanding can inform contingency planning for satellites, navigation systems and power-grid resilience when the next major geomagnetic storm occurs.