Earth’s Own Air Fueled 85% of Particles in May 2024 Solar Superstorm

Earth’s own atmosphere may have helped turn the May 2024 solar storm into one of the most powerful in decades, according to a study in Science Advances. Satellite measurements showed that roughly 85% of the charged particles fueling the disturbance came from Earth’s upper atmosphere, not from the Sun, Nagoya University said in a release carried by ScienceDaily.

Researchers also detected an extraordinary 40% weakening of Earth’s magnetic field high above the planet during the event.

What happened in May 2024?

A large sunspot released several powerful eruptions in rapid succession. The clouds of magnetized plasma combined before hitting Earth’s magnetosphere, the region controlled by the planet’s magnetic field. The result, on May 10 and 11, was one of the strongest geomagnetic storms in decades, known as the “Gannon storm” or “Mother’s Day storm.” It sent auroras across skies in places where northern and southern lights are rarely seen.

It pushed a measure of geomagnetic disturbance called the SYM-H index to a minimum of −518 nanotesla. That is the second-largest disturbance recorded since 1981. The previous storm of comparable strength came in November 2004. The storm also produced the strongest magnetic disturbance ever measured in the ring current, a vast belt of electrically charged particles around Earth.

What did the researchers find?

For decades, scientists have debated where ring current particles come from. Two sources are known: the solar wind and Earth’s ionosphere, an electrically charged layer of the upper atmosphere. Some researchers expected the solar wind to remain important in an extreme event with particularly dense solar wind.

Japan’s Arase satellite, launched in 2016 and operated by the Japan Aerospace Exploration Agency, flew through the ring current region shortly after the storm began and again as it neared its peak. Its instruments can measure both the mass and energy of individual ions. Lead author Naritoshi Kitamura of Nagoya University called it the first simultaneous observation of ring current ions and solar wind during a storm this large. He said approximately 85% of the ions were oxygen from Earth’s own ionosphere.

Why would that make the storm stronger?

The ions from Earth are much heavier than those supplied by the solar wind. According to the release, that may have strengthened the magnetic disturbance and caused the ring current to reach its greatest intensity unusually close to the planet. The findings suggest the atmosphere may play a much larger role in the severity of extreme geomagnetic storms than scientists had recognized. The release describes this as a possibility rather than a settled conclusion.

Why does it matter?

Storms like this are more than light shows. Kitamura said some super or extreme storms pose radiation risks to spacecraft, disturb GPS signals and communications, and cause power outages. Knowing how a storm develops is therefore a practical question as well as a scientific one.

The ring current’s ions circle the planet and generate their own magnetic field, which partly opposes Earth’s natural field and weakens the field measured at ground level. Scientists use those changes as a key signal of a storm’s strength.

What comes next?

The result strengthens the case for a proposed Japanese satellite mission designed to study how particles from the atmosphere enter space and influence powerful geomagnetic storms.

Around Prague, based on reporting by ScienceDaily

Cover photo: NASA Johnson Space Center / Wikimedia Commons (public domain)

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