Question
What does the K-index measure?
Answer Options
- A) The relative position of sunspots on the surface of the Sun
- B) The short-term stability of Earth’s geomagnetic field
- C) The short-term stability of the Sun’s magnetic field
- D) The solar radio flux at Boulder, Colorado
Correct Answer: B
Explanation
The K-index is a scale ranging from 0 to 9 used to characterize the activity of the Earth’s magnetic field (geomagnetic field). Specifically, it measures the short-term stability (or disturbance) of this field over a three-hour period.
A low K-index (0 to 2) indicates a quiet, stable field, which generally correlates with good, predictable HF propagation. A high K-index (4 or higher) indicates a disturbed or stormy field, which often means poor or unstable HF propagation conditions due to increased ionospheric absorption and turbulence.
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