Glossary of terms

Item Element Description
SFI Solar Flux Index DRAO Penticton reported value from 62.5 to 300. Intensity of solar radiation measured at 2800MHz (10.7cm). Good indication of the F layer ionization (layer that gives us most of our DX on HF). The higher the number, the greater the level of ionization is, and the higher the frequency. Measured three times daily, and the last received value is reported. Note that NOAA recorded SFI for the day is the 2nd (or middle) of these readings, and may be different than the last recorded reading displayed on the banners. SFI does correlate to 304A (see graph below).
SN Sunspot Number NOAA reported value from 0 to 250. Daily Sunspot Number provided by NOAA is computed using a formula [R=k (10g+s)] by Rudolph Wolf in 1848, where R is the sunspot number; g is the number of sunspot groups on the solar disk; s is the total number of individual spots in all the groups; and k is a variable scaling factor (usually <1) that accounts for observing conditions and the type of observing device. SN does loosely correlate to SFI. Updated once daily.
A Planetary A Index NOAA reported value from 0 to 400. Provides a daily average level for geomagnetic activity. Uses the average of eight 3 hour K-Index values (magnetic value measured in nanotesla or nT) to provide the level of instability in the earth’s geomagnetic field. When used with K-Index: Both high indicates geomagnetic field is unstable, and HF signals are prone to sudden fades, and some paths may close while others open up abruptly and with little warning. High K index/Low A indicates a sudden, abrupt disturbance in the geomagnetic field, which can cause an intense but brief disruption in HF propagation, but can cause an auroral event. Updated once daily.
K Planetary K Index NOAA reported value from 0 to 9. Measures disturbances in the horizontal component of earth's magnetic field. Value in nT is measured using a magnetometer during a three-hour interval, and then converted to a factor. Use with A-Index – sees above to determine HF conditions. Updated eight times daily.
Data from n0nbh