X-Ray Flares (A/B/C/M/X) and the NOAA R-Scale Explained

X-Ray Flares (A/B/C/M/X) and the NOAA R-Scale ExplainedHow GOES X-ray flux classifies solar flares, the A/B/C/M/X scale, what M- and X-class flares do to daytime HF (sudden ionospheric disturbances), and the NOAA R-scale.Solar flares are brief intense bursts of X-ray and ultraviolet radiation. GOES X-ray flux classifies their strength. Large flares produce sudden ionospheric disturbances (SIDs) that knock out daylit HF bands.Class systemEach class is a 10x step in peak X-ray flux (1-8 A channel):

A: < 1e-7 W/m^2, background

B: 1e-7 to 1e-6, minor

C: 1e-6 to 1e-5, common

M: 1e-5 to 1e-4, daytime HF blackouts

X: > 1e-4, major widespread blackout

R-scaleNOAA radio blackout scale 1-5. R1 ~ M1+, R2 ~ M5+, R3 ~ X1+, R4 ~ X10+, R5 ~ X20+.Part of the BloomWX learn library — beginner-friendly explainers covering every surface of the BloomWX weather dashboard. Open BloomWX to see live data for any U.S. county.