Overview
- Japan’s Arase spacecraft recorded a sudden surge of ultra‑relativistic electrons well inside the previously identified barrier, with fluxes at about 3 MeV rising by roughly 5,000 times during the May 2024 superstorm.
- Researchers used electron phase space density to show a growing local peak near the barrier, which indicates the particles were energized in place rather than simply transported inward from the outer belt.
- Arase detected intense upward‑sweeping 'chorus' electromagnetic waves that can transfer energy to electrons, and the team links those waves to local acceleration under low plasma conditions.
- The May 2024 storm severely eroded the plasmasphere, leaving the region depleted for about 4.3–4.7 days and creating the low‑density environment that let chorus waves operate efficiently.
- Miyoshi et al. published the consolidated results in Geophysical Research Letters in October 2026 and warned that these processes can create months‑long radiation hazards for satellites and that forecasting and mitigation practices need updating.