SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hamg-flare-eight-minutes

How long does it take solar flare radiation to start affecting radio propagation on Earth?

About 8 minutes, the travel time of light.

Start playing free

  1. 8 minutes ✔
  2. 1 to 2 hours
  3. 28 days

Why: The ultraviolet and X-ray burst from a flare travels at the speed of light. It arrives in about 8 minutes and can quickly disrupt daytime HF signals.

Huh, didn't know that: A coronal mass ejection is much slower and takes 15 hours to several days to affect propagation.

The dad joke
Why did the solar flare get a speeding ticket? It arrived in 8 minutes flat.
Like this card?
Play the game

References

Answer: 8 minutes. The ultraviolet and X-ray burst from a flare travels at the speed of light. It arrives in about 8 minutes and can quickly disrupt daytime HF signals.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    8 minutes
    Checked 2026-10-10.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

Ham RadioOn which HF bands do General licensees have some off-limits portions?Ham RadioOn which of these bands is voice (phone) operation prohibited?Ham RadioWhat must hams do when the amateur service is a secondary user on a band?

That's stuff everyone should know.