Measurements from Japan’s Arase satellite show that Earth’s upper atmosphere supplied more than 85% of the ring current’s ions during the May 2024 superstorm, a finding that could change how scientists assess extreme space weather.
The international research team, led by Nagoya University, analyzed ions measured near Earth and observations of the solar wind. The solar wind delivered the energy that drove the storm. But it contributed very little to the ring current’s ions, even though it was unusually dense.
The measured ions had energies from 9.6–184.2 kiloelectronvolts. Most came from Earth, especially heavy ions that rose from the ionosphere, the electrically charged upper atmosphere. The ring current is a belt of charged particles circling Earth that helps drive magnetic disturbances around the planet.
The storm hit on May 10 and 11, 2024. It reached a SYM-H index of minus 518 nanotesla, the second-lowest reading recorded since 1981. The researchers say heavy ions from Earth may have helped make the disturbance stronger.
They may also have brought the ring current unusually close to the planet. The study reports that the intense current deformed Earth’s magnetic field. It also reports that the current contributed to losses of electrons in the radiation belts.
The results suggest that scientists should investigate the atmosphere’s supply of ions when improving forecasts of the strongest storms.