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Beginner · 5 min

What a Solar Flare Is

Distinguish a burst of radiation from a cloud of solar material.

Follow these steps

  1. 1

    A solar flare is a sudden release of magnetic energy that heats plasma and emits radiation.

  2. 2

    A coronal mass ejection, or CME, is expelled material carrying magnetic field. A flare and a CME can occur together, but they are different phenomena.

  3. 3

    NOAA’s R scale concerns radio blackouts, S concerns solar radiation storms, and G concerns geomagnetic storms.

  4. 4

    Check the observation time and the instrument. Extreme-ultraviolet solar images use scientific false colors.

  5. 5

    Read official NOAA forecasts and bulletins before assuming an eruption will affect Earth.

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Why this matters

A flare is a burst of light and radiation. It reaches Earth in about 8 minutes and can cause short radio blackouts on the side of Earth facing the Sun.

A coronal mass ejection (CME) is a cloud of solar material. It usually takes one to three days to reach Earth, and it is what drives most geomagnetic storms and auroras.

Flare classes go A, B, C, M, X, and each letter is 10 times stronger than the one before. NOAA links flare strength to its R (radio blackout) scale: about M1 is R1, M5 is R2, X1 is R3.

A strong flare is not the same as a storm

A fictional report says: "M5.2 flare observed at 14:05 UTC."

  1. Flare class M5 matches NOAA R2 (Moderate): a radio blackout is possible on Earth’s sunlit side for minutes to hours.
  2. The report says nothing about a CME. A geomagnetic storm (G scale) needs a separate NOAA watch or warning.
  3. Next step: check NOAA’s current alerts before repeating any "solar storm will hit Earth" claim.

Try it yourself

Sort today’s space weather into flare, radiation storm and geomagnetic storm.

  1. Open EarthWatch and find its solar or space-weather information. Write down the latest flare class and its observation time, or "none listed."
  2. Open NOAA’s space weather phenomena page and find the R, S and G scales.
  3. For each scale, write the current level if one is listed, or "none."
  4. Write one sentence: does today’s information show a flare, a CME, both or neither?

Expected result: A note like "Latest flare M1.3 at 09:12 UTC; R1; S none; G none; flare only." "None listed" is a valid answer on a quiet day.

Check your understanding

You can explain why a bright solar image alone doesn’t mean an Earth-directed CME, a power outage or satellite damage.

If you get stuck

The solar image colors look alarming.

Extreme-ultraviolet images use scientific false colors chosen to show different temperatures. The color is not a danger level.

A headline says a storm is "hitting Earth" but NOAA shows no G watch.

Rely on NOAA’s official alerts. Headlines often mix up flares and CMEs.

I can’t find the flare class.

Look for a letter and number such as C4.1, M2.0 or X1.5 next to the observation time.

The times don’t match my clock.

Space-weather reports usually use UTC. Convert to your local time.

Official sources

Keep a useful prompt handy

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