Our local star the Sun is a vast sphere of electrically charged gas (plasma) and is the beating heart of our Solar System, bathing our world in life giving heat and light 150 million kilometres away. A main-sequence star, it’s composed primarily of hydrogen and helium, converting four million tons of matter into energy every second through nuclear fusion in its core. With surface temperatures reaching 5,500°C and a diameter 109 times that of Earth, the Sun has illuminated our planet for 4.6 billion years and will continue to shine for (hopefully) another 5 billion more before expanding into a red giant.
The Sun in white light showing sunspots and faculae
Of the many events visible on the Sun, solar storms are powerful eruptions of energy from that hurl charged particles and electromagnetic radiation into space at tremendous speeds. These violent phenomena begin as solar flares or coronal mass ejections (CMEs) on the Sun’s visible surface, where magnetic field lines twist, break, and explosively reconnect. When directed toward Earth, these storms can interact with our planet’s magnetic field, triggering geomagnetic disturbances that create spectacular auroras but also pose serious risks to modern infrastructure.
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Solar Orbiter view of the Sun showing solar flares
A year ago, NASA and other government agencies gathered to simulate responding to such events due to the potential risks yet their simulations were interrupted by the most powerful solar storm in over two decades. The G5 level event that was named the Gannon storm (named after space weather physicist Jennifer Gannon,) struck Earth on 10 May 2024. It transformed their tabletop exercise into a real-world response. While this powerful solar event—capable of damaging satellites, overloading electrical grids, and endangering astronauts—didn’t cause catastrophic damage, it provided valuable insights to help prepare for future solar threats.
The storm caused widespread disruptions on Earth and in space. High-voltage lines tripped and transformers overheated in the US and GPS-guided tractors went off course. In the air, increased radiation risk and communication issues forced trans-Atlantic flights to reroute. The storm also heated the thermosphere to over 1,100°C, causing it to expand and create strong winds that pushed heavy nitrogen particles higher. This expansion increased atmospheric drag on satellites, causing some to lose altitude or deorbit early, and forcing others to use more power to stay in orbit and avoid debris.
“Not all farms were affected, but those that were lost on average about $17,000 per farm” – Terry Griffin, a professor of Agricultural Economics at Kansas State University.
Rare global auroral displays were also triggered, with over 6,000 sightings reported from 55 countries across all continents. In Japan, unusually high magenta auroras puzzled scientists until they found, through photo analysis, that these lights appeared about 600 miles above Earth—much higher than usual. A study concluded the rare colour came from a mix of red and blue auroras caused by oxygen and nitrogen molecules lifted by the storm’s heating and expansion of the upper atmosphere. NASA called it a unique and exceptional event.
The Sun’s intense activity didn’t just affect Earth—it also hit Mars. NASA’s MAVEN spacecraft observed auroral displays covering Mars between May 14 and 20. The solar particles disrupted the star camera on the Mars Odyssey orbiter, causing it to shut down temporarily, and create visual “snow” in images from Curiosity’s cameras. Most notably, Curiosity recorded its highest-ever radiation spike, with levels that would have exposed astronauts to the equivalent of 30 chest X-rays.
The launch of MAVEN by an Atlas V rocket on 18 November 2013 (Credit : NASA)
The Gannon storm stands as a stark reminder of the Sun’s immense power, spreading aurora to unusually low latitudes and earning the title of the best-documented geomagnetic storm in history. It has provided an unprecedented set of data that scientists are still analysing a year later. From unexpected radiation surges on Mars to tractor disruptions in the American Midwest, the storm highlighted both the beauty and the vulnerability of life under the influence of our local star. As researchers continue to unravel the Gannon storm’s many effects, the lessons learned will shape future strategies for protecting technology, infrastructure, and even astronauts from the Sun.
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