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SESK: Stuff Everyone Should Know · sesk.info/hame-flare-class-steps

Each solar flare X-ray class (A, B, C, M, X) is how many times stronger than the one before?

10 times stronger at each step.

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  1. 2 times
  2. 100 times
  3. 10 times ✔

Why: NOAA lists the flare classes as A, B, C, M and X, each ten times higher than the last. X flares reach 10 to the minus 4 watts per square meter.

Huh, didn't know that: M flares are 10 to the minus 5 W/m2, so an X flare is ten times an M flare.

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References

Answer: 10 times. NOAA lists the flare classes as A, B, C, M and X, each ten times higher than the last. X flares reach 10 to the minus 4 watts per square meter.

  1. NOAA SWPC Solar Flares / Radio Blackouts www.spaceweather.gov/phenomena/solar-flares-radio-blackouts
    The next level, ten times higher, is the “B” level
    Checked 2026-10-11.
  2. NOAA SWPC Solar Flares / Radio Blackouts www.spaceweather.gov/phenomena/solar-flares-radio-blackouts
    “M” flares (10^{-5} W/m^{2})
    Checked 2026-10-11.

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