Classification by X-Ray Flux
Flares are classified by their X-ray flux (0.1–0.8 nm) into A, B, C, M, and X. Each class is 10 times more intense than the previous. A is weakest; X is strongest. A number (e.g. X1.5, M7) gives finer scale within the class. M and X flares can cause significant ionospheric effects and radio blackouts; X-class flares are the most powerful and are more common near solar maximum. Cosmic Radar lists reported flares in the daily report with space weather and Kp.
Sources and further reading
- NOAA – Solar flare classification – X-ray classes and effects
- NASA SDO – Real-time flare imagery