In May 2024, Earth was struck by a rare G5 – Extreme geomagnetic storm, the strongest recorded in over twenty years. The storm was triggered by a series of powerful solar flares and coronal mass ejections (CMEs) from Active Region 3664 and was named the Gannon storm in tribute to space weather expert Jennifer Gannon. While it didn’t cause catastrophic damage, it left scientists with a lot to unpack.
Since then, data and observations from that event have helped in advancing efforts to better anticipate and manage extreme geomagnetic disturbances. There was no large-scale disaster, but the storm left its mark in many ways. From subtle disruptions to noticeable failures, its effects were felt both in space and on the ground.
Power glitches and travel disruptions on Earth
The storm triggered a mix of electrical issues across parts of the Midwestern U.S. A few high-voltage lines went offline, some transformers ran too hot, and unmanned Global Positioning System (GPS) guided tractors struggled to stay on track.
This severely disrupted the planting season, which had already been delayed by a wet spring. The impact varied by region, with farms relying heavily on GPS-guided equipment experiencing the most significant delays. While exact per-farm losses are unclear, some estimated place damage at USD 17 000 per farm, while national estimates suggest the agricultural sector incurred up to USD 500 million in damages.
Air travel wasn’t spared either. With rising radiation levels and patchy signals posing risks, several trans-Atlantic flights had to be rerouted mid-journey to keep crews and passengers safe.
Although the additional radiation exposure remained within safe thresholds, disruptions to GPS and high-frequency radio systems over polar routes prompted precautionary diversions to ensure crew and passenger safety.
Gannon storm effects from terrestrial infrastructure to planetary orbit
The storm caused a sharp rise in temperature in Earth’s thermosphere. Normally topping out near 649°C (1 200°F) at about 161 km (100 miles) up, temperatures surged past 1 149°C (2 100°F) during the event. National Aeronautics and Space Administration’s (NASA) Global-scale Observations of the Limb and Disk (GOLD) mission tracked the rapid expansion of this heated layer, which sent dense nitrogen particles climbing higher than usual on the back of powerful winds.
It disrupted low-Earth orbit in several ways. As the atmosphere expanded, drag increased, slowing down many satellites. NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) lost elevation and switched to safe mode. Colorado Inner Radiation Belt Experiment (CIRBE), a small research satellite, was pulled out of orbit months earlier than planned. European Space Agency’s (ESA) Sentinel satellites used more fuel than usual to adjust their paths and avoid debris.
The ionosphere also changed shape. A dense layer that normally sits over the equator at night dipped far south, creating a strange check-mark pattern and a temporary gap near the equator.
NASA’s Magnetospheric Multiscale (MMS) and Time History of Events and Macroscale Interactions-Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (THEMIS-ARTEMIS) missions recorded large, coiled waves of particles moving along the front of the solar eruptions. These spiraling structures funneled energy and plasma into the magnetosphere again and again. Each surge added to the buildup, triggering the most powerful current measured in that region in two decades.
During the storm, CIRBE detected two new bands of high-energy particles that briefly appeared between Earth’s permanent Van Allen radiation belts (named after American physicist James Van Allen). The temporary belts didn’t stick around, but their presence mattered. Packed with fast-moving electrons and protons, they posed a potential hazard to satellites and crews in orbit.
Credit: NASA/Goddard Space Flight Center/Kristen Perrin
NASA’s Aurorasaurus project received over 6 000 reports from observers in 55 countries, including sightings from every continent. In Japan, the lights took on an unusual magenta hue.
Curious about the color shift, scientists analyzed hundreds of photos and discovered that the auroras had formed around 966 km (600 miles) higher than usual. The rare magenta auroras were caused by a blend of red and blue light from oxygen and nitrogen pushed to higher altitudes by the storm-heated atmosphere.
Mars’ response to extreme solar activity
Between May 14 and 20, as the region that sparked the storm on Earth redirected toward Mars, NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) orbiter captured stunning auroras as solar particles interacted with the atmosphere of Mars.
NASA’s 2001 Mars Odyssey orbiter also suffered, as solar particles caused a temporary shutdown of the star camera for an hour. On Mars’ surface, Curiosity’s navigation cameras showed streaks from charged particles. Its Radiation Assessment Detector (RAD) recorded the highest radiation levels (8 100 micrograys) since 2012.
The Gannon storm stands as the most documented and studied geomagnetic event in history, with data collected expected to be analyzed for years to come.