Glossary

A index

A daily indicator of geomagnetic activity.

LevelIndex range
Quiet0–7
Unsettled8–15
Active16–29
Minor storm30–49
Major storm50–99
Severe storm100–400

You can find a detailed description of how the A index is calculated and how its values are related to radio signal propagation conditions in the Solar Guide Page on the Web, published by Radio Netherlands’ Media Network.

CIRAF zone

A means for indicating a shortwave broadcast target area, devised by the International Telecommunication Union, Radio division. The world area is divided into a total of 85 zones. Please see the CIRAF Zones reference list in this online help, and visit the ITU‑R broadcast reference data page, which provides some CIRAF Zone maps Page on the Web.

Gantt chart

A graphic representation of schedule information. On a Gantt chart, activities are listed down the left side of the chart, dates are displayed across the top, and activity durations are displayed as time‐placed horizontal bars. Also referred to as the bar chart.

K index

A 3‑hourly indicator of geomagnetic activity.

LevelIndex valueCorresponding A index value
Quiet00
Quiet13
Quiet27
Unsettled315
Active427
Minor storm548
Major storm680
Severe storm7140
Severe storm8240
Severe storm9400

You can find a detailed description of how the K index is calculated and how its values are related to radio signal propagation conditions in the Solar Guide Page on the Web, published by Radio Netherlands’ Media Network.

MiniMUF

A classic algorithm for computing MUF values on mini‐computers. The original MiniMUF formulae were presented in the QST magazine: Rose, Robert B., “MINIMUF: A simplified MUF‑Prediction Program for Microcomputers”, QST December 1982, pages 36–38.

MUF

Maximum Usable Frequency—the maximum frequency on which high frequency radio signal propagation is possible. MUF depends on the time of year, on the time of day at the transmitter and receiver locations, and on the current solar conditions.

Solar flux

An indicator of the intensity of solar radio emission.

You can find a detailed description of how the solar flux is measured and how its values are related to radio signal propagation conditions in the Solar Guide Page on the Web, published by Radio Netherlands’ Media Network.