The Sun emitted significant M-class solar flares on April 19th and 20th, 2025, with the strongest reaching M4.4 class. M-class flares can cause brief radio blackouts, especially in polar regions, and minor radiation storms that pose risks to astronauts, according to the European Space Agency (ESA).
These flares are classified based on X-ray wavelength intensity, with M-class flares being medium-sized, according to NASA. They are less powerful than X-class flares but can still trigger coronal mass ejections (CMEs), which are large releases of plasma and magnetic fields that can disrupt Earth's magnetosphere, according to Space.com.
A G4 (severe) geomagnetic storm impacted Earth around April 16th, resulting in auroras visible across various regions, including Tatarstan, Moscow, and parts of Europe and North America, as reported by Space.com and NOAA. The geomagnetic activity was associated with CMEs that reached Earth on April 15th, and while the storm's strength weakened, there remained a chance of further G1-G3 level activity.