Heavy oxygen ions from Earth’s own atmosphere unexpectedly accounted for roughly 85 percent of the particles in the ring current during the extreme May 2024 solar superstorm, according to ScienceDaily, overriding the solar wind contributions traditionally thought to drive such geomagnetic disturbances.
The disturbance pushed the SYM-H index to a minimum of −518 nanotesla on May 10 and 11, 2024, marking the second-largest recorded geomagnetic disruption since 1981. This severe event followed a comparable disturbance in November 2004.
“Some super or extreme geomagnetic storms are not just impressive light shows — they pose radiation risks to spacecraft, disturb GPS signals and communications, and cause power outages. Understanding how a geomagnetic storm develops is not only a scientific question, but also one with real-world consequences,” said Naritoshi Kitamura, designated assistant professor from the Institute for Space-Earth Environmental Research at Nagoya University.
Japan’s Arase satellite, launched in 2016 by the Japan Aerospace Exploration Agency, captured simultaneous observations of ring current ions and solar wind during the height of the solar event. The spacecraft travels through the region where the ring current forms.
“This is the first simultaneous observation of ring current ions and solar wind during a storm this large, and the data was clear — approximately 85% of ions were oxygen from Earth’s own ionosphere,” Kitamura told ScienceDaily.
The dense solar wind material arriving from the Sun contributed very few particles to the measured population. Instead, heavy ions from Earth's upper atmosphere dominated the ring current more than ever before.
Near the peak of the storm, Arase detected a 40 percent decrease in magnetic field intensity at roughly 16,000 kilometers above Earth. This dramatic reduction occurred much closer to the planet than similar large decreases previously documented.
At the same time, the satellite detected a decline in energetic electrons circulating through the region. Scientists have not yet determined whether the deformation of the magnetic field directly caused this electron loss.
The findings, published in ScienceAdvances, suggest that heavy atmospheric ions caused the ring current to reach maximum intensity unusually close to Earth. Current forecasting models rely primarily on solar wind conditions to estimate storm power.
The new measurements indicate that conditions within Earth’s upper atmosphere influence a storm’s eventual intensity. Understanding how atmospheric ions escape into the magnetosphere remains essential for improving space weather predictions.
These findings support FACTORS, a proposed mission involving two satellites being prepared for an upcoming JAXA proposal opportunity. The mission would investigate how ions from Earth’s atmosphere flow into the magnetosphere.
Researchers will need further study to establish how magnetic field deformation directly relates to electron loss.
