What is a Solar Flare?
A solar flare is a sudden, bright eruption in the Sun's atmosphere, often near sunspots. It releases energy across the electromagnetic spectrum—from X-rays and UV to visible light. Flares are caused by the reconnection of magnetic field lines, which accelerates particles and heats the plasma. The radiation reaches Earth in about 8 minutes and can cause ionospheric disturbances, radio blackouts, and in rare cases effects on satellites.
Classification: A, B, C, M, X
Flares are classified by their X-ray flux (measured in the 0.1–0.8 nm band) into classes A, B, C, M, and X. Each class is about 10 times more intense than the previous. A is the weakest; X the strongest. Within each class, a number (e.g. X1.5, M7) gives finer scale. M- and X-class flares can cause significant radio blackouts and are more common near solar maximum. Cosmic Radar lists reported flares in the daily report together with CMEs and the Kp index.
Sources and further reading
- NOAA SWPC – Solar flares – Flare classification and effects
- NASA SDO – Real-time solar images and flares
- ESA – Space weather – European monitoring