Earth just faced the strongest solar radiation storm in over 22 years—here's what you need to know

Earth endured its most intense solar radiation storm in over 22 years on January 19, 2026, a day after a powerful X1.9-class solar flare from sunspot region AR4341 triggered an R3 radio blackout within the Arctic region. NOAA’s Space Weather Prediction Center classified the event as S4, making it a severe solar radiation storm. This S4-class radiation storm surpassed the infamous “Halloween storms” from October 2003 in proton flux intensity, as measured by the Geostationary Operational Environmental Satellite (GOES-19). A solar radiation storm is characterized by charged particles, such as protons, racing at near-light speeds and impacting satellites and polar flights in a matter of minutes after being ejected from the sun.  

According to the SWPC, a G-4 (severe) geomagnetic storm alert was also issued for January 20, 2026. This resulted in the visibility of aurora across multiple US states, even in places where such events are rare, on January 20 and 21. Data from Spaceweather.com in relation to the coronal mass ejection (CME) impact in the late hours of January 19 also supported the G4 storm event alerts, adding that the storm is set to continue into January 21.

Space weather events such as these have been all too common in the past few months, with a strong X5-class solar flare in early November, followed by a G4 geomagnetic storm, resulting in aurora sightings beyond the usual confines of northern latitudes.

Solar flares, like the one on Sunday and the similarly rated solar flare from November 30, 2025, erupt as sudden releases of radiation that span across the entire width of the electromagnetic spectrum—including X-rays, radio waves, gamma rays, ultraviolet, and visible light. They are categorized as A, B, C, M, and X-class, with the latter having a 10-fold increase in energy over the preceding class, i.e., M-class, according to NASA. They are the most powerful explosions in the solar system, having enough energy to match a billion hydrogen bombs. Meanwhile, CMEs, or coronal mass ejections, are eruptions of plasma from the sun’s outer atmosphere, the corona. These are what are directly responsible for geomagnetic storms and occurrences of aurora.

Though linked with CMEs and solar flares, solar radiation storms happen when charged particles such as protons and electrons are ejected into space at extremely high velocities, often traversing the distance to Earth in a matter of minutes. They have the capability of penetrating the Earth’s protective magnetosphere by following the magnetic field lines at the north and south magnetic poles, possibly reaching the surface. 

Solar radiation storms and their constituent particles can ionize atmospheric molecules and atoms by removing electrons, which affects high-frequency radio communications. They can also degrade satellite hardware, such as solar panels and electronic circuits. What’s worse, they pose radiation risks to current crew members aboard the International Space Station and those in polar missions, as high-speed particles from solar radiation storms can penetrate human tissue.

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