Extra exam question E3C01
Subelement E3, RADIO WAVE PROPAGATION· Group E3C
What is the cause of short-term radio blackouts?
- A.Coronal mass ejections
- B.Sunspots on the solar equator
- C.North-oriented interplanetary magnetic field
- D.Solar flares (correct answer)
WhyShort-term radio blackouts are caused by solar flares. Short-term HF radio blackouts are caused by solar flares, sudden bursts of X-ray and ultraviolet radiation from the sun that spike ionization in the D region and dramatically increase absorption of HF signals passing through it, answer D. Coronal mass ejections, sunspot location, and the orientation of the interplanetary magnetic field are all related space-weather factors, but the specific, sudden blackout described here is a flare effect, not any of the others.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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