The Solar Astronomy Laboratory of the Space Research Institute of the Russian Academy of Sciences has detected an S4-level radiation storm in the vicinity of Earth, the most powerful in the past two solar cycles. The laboratory reported this in a statement published on its official Telegram channel.

According to the scientists, the flux of solar protons has exceeded 10,000 units. This marks the first time in two full solar cycles that a radiation storm of level S4 has been observed near Earth. They noted that level S5 exists only theoretically and has never been reached in the modern history of observations.

Until now, the strongest known event of this kind dated back to the previous century, when proton flux levels reached about 40,000 units.

What Triggered the Storm

On January 19, the Sun produced a class M1.20 flare at 14:19 Moscow time. Another flare, class C2.83, peaked at 15:27 the same day. These events were part of the activity of a large and highly active region on the Sun that rotated into Earth’s view in mid-January.

Earlier, on January 12, the Solar Astronomy Laboratory had warned that a powerful active region on the far side of the Sun, where two flares believed to be of class X had already occurred, would soon become visible from Earth. That region has now fully rotated into view, and its effects are manifesting as an unprecedented radiation storm.

Effects on Earth and Technology

Radiation storms of level S4 can cause serious disturbances to satellites, especially those in low Earth orbit. Senior researcher Anton Reva from the Space Research Institute and the Institute of Solar-Terrestrial Physics compared the effect on electronics to placing a computer close to the core of a nuclear reactor. Streams of electrons, gamma radiation, and energetic protons can damage or disrupt onboard systems.

At the same time, modern satellites are designed with strong radiation shielding and radiation-hardened components. According to Reva, this protection significantly reduces the risk of major failures, so large-scale disruptions are unlikely.

In addition to the radiation storm, a geomagnetic storm triggered by the associated plasma ejection has already reached level G4, which is classified as “very strong.” This may lead to disturbances in radio communications, satellite operations, and radio-frequency navigation systems.

Senior researcher Natan Eismont from the Space Research Institute noted that such geomagnetic events can affect the well-being of some people, particularly those who are meteorologically sensitive. However, he emphasized that this group represents only a minority of the population.

In Brief

On January 20, 2026, Earth is being impacted by an S4-level radiation storm, the strongest in two solar cycles, with a proton flux exceeding 10,000 units. The event was caused by powerful solar flares from a highly active region that recently rotated into view. The associated geomagnetic storm has already reached level G4, potentially causing disruptions to communications and navigation systems. For most people the threat is minimal, but satellites and meteorologically sensitive individuals may experience noticeable effects. Observations are ongoing, as this is a rare and scientifically significant event in the study of solar activity.