By Kurtis Archer | 2025-05-21

Scientists are still examining data and learning from the spectacular geomagnetic storm that awed astronomers and sky watchers last May.

The Gannon storm lit up auroras across the world May 8-11, 2024, and was classified as a G5 -- the highest on the National Oceanic and Atmospheric Administration (NOAA)'s space weather scale.

Sunspot clusters 17 times as wide as Earth produced solar flares that created the geomagnetic storm, lighting up the night sky with fantastic colors in areas on Earth rarely known to witness such activity.

At least eight large blasts of magnetic field and plasma, known as coronal mass ejections, shot from the Sun toward Earth.

The Gannon storm was the first geomagnetic storm to receive an official name. NASA named it after Jennifer Lea Gannon, a space weather physicist who died in May 2024.

Preparation essential

"The Gannon storm was a spectacular event in the sense that so many people got to see the aurora, especially those living in areas that don't typically see it," Mike Cook, space weather lead at MITRE Corporation, told Space.com.

"But, beyond that, it was a reminder that our sun is capable of producing these very disruptive events that can impact our critical infrastructure," he said.

Forecasters at NOAA's Space Weather Prediction Center (SWPC) were able to preemptively warn power grid operators and ensure the solar storm disrupted civilization's needs and activities as little as possible.

"More than 10 years of planning and preparation paid off," said Clinton Wallace, director of the SWPC.

"Thanks to early warnings and strong teamwork, the people who run critical systems like power, farming and satellites were able to prevent most of the damage from the May 2024 storm," he told Space.com.

Learning more about space weather and its impact on terrestrial daily lives is essential, analysts say.

"Even though the grid successfully avoided a failure of such magnitude, it did show that the general public should understand that a power blackout could occur with future storms of this or stronger magnitude," warned Shawn Dahl, service coordinator at the SWPC.

"Press and media are becoming more knowledgeable, and emergency management authorities are increasingly planning for space weather storms," Dahl told Space.com. "This is a very good thing and helps prepare our nation's resilience."

Impact on the ground

Tamitha Skov, a retired research scientist and former space weather professor, pointed out some surprising challenges that came as a result of the storm.

For example, the agriculture industry suffered as some Global Positioning System (GPS) devices that guide tractors were disrupted.

"We have known about GNSS [Global Navigation Satellite System] vulnerability for decades; however, it is now so integrated into precision farming equipment and practices that a loss of quality signal from satellites can cause an entire agriculture industry to halt for the duration of the storm," Skov told Space.com.

"A few days outage might not seem to be a big deal, but when the storm hits during planting or harvest season, as big storms typically do (storm effects are enhanced at the equinoxes), then the impact to the crop yield can be extremely significant," she added.

In the Midwestern United States, GPS-guided tractors veered off course, further disrupting planting that had already been delayed by heavy rains that spring, NASA reported May 9.

"Not all farms were affected, but those that were lost on average about $17,000 per farm," said Terry Griffin, a professor of agricultural economics at Kansas State University. "It's not catastrophic, but they'll miss it."

Some high-voltage lines automatically cut electricity as a safety measure, and transformers overheated.

Impact in the sky

The Gannon storm trapped high-energy electrons and protons around the Earth between the existing Van Allen radiation belts, creating new but temporary belts.

As a result, airlines redirected several transatlantic flights between May 11-18, 2024, because of concerns over rising radiation levels -- which scientists ultimately determined to be safe -- and over communication disruptions.

Many satellites switched to safe mode because atmospheric drag caused them to lose altitude, while others used more fuel than usual raising their orbit and maneuvering around debris. One owner deorbited a satellite months earlier than planned.

Earth's ionosphere changed shape. A dense part normally at the equator shifted southward, creating a temporary gap near the equator.

The thermosphere, Earth's upper atmospheric layer, saw its peak temperatures at 100 miles up rise from its usual 1,200 degrees Fahrenheit to more than 2,100 degrees.

This surge of heat expanded the atmosphere and created strong winds that carried heavy nitrogen particles higher than they would normally travel. This expanding atmosphere is what caused increased atmospheric drag on satellites.

Beyond Earth

Extreme solar storms could pose serious threats to astronauts during spacewalks and can impact various spacecraft systems.

The Gannon storm eventually rotated away from Earth and redirected its outbursts toward Mars.

"As energetic particles from the Sun struck the Martian atmosphere, NASA's MAVEN (Mars Atmosphere and Volatile Evolution) orbiter watched auroras engulf the Red Planet from May 14 to 20," the space agency reported.

"Solar particles overwhelmed the star camera on NASA's 2001 Mars Odyssey orbiter (which uses stars to orient the spacecraft), causing the camera to cut out for almost an hour," it said.

Meanwhile, NASA's Curiosity rover Radiation Assessment Detector recorded the biggest surge of radiation since the rover landed in 2012.

"If astronauts had been there, they would have received a radiation dose of 8,100 micrograys -- equivalent to 30 chest X-rays," NASA said.