General exam question G3A12
Subelement G3, RADIO WAVE PROPAGATION· Group G3A
G3A12
What does the K-index measure?
- A.The relative position of sunspots on the surface of the Sun
- B.The short-term stability of Earth’s geomagnetic field (correct answer)
- C.The short-term stability of the Sun’s magnetic field
- D.The solar radio flux at Boulder, Colorado
WhyThe K-index measures the short-term stability of Earth's geomagnetic field. The K-index tracks short-term (typically 3-hour) stability of Earth's own geomagnetic field, a quick-moving indicator of current disturbance level, answer B. It doesn't describe sunspot positions on the Sun, the Sun's own magnetic field stability, or a solar radio flux measurement, those are each tracked by different indices.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2023-2027 NCVEC Element 3 pool (public domain); the explanation above is original writing, see our methodology.
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