What SunSpot Number indices should be used.
NOAA has changed how they put out the Ionospheric indices that are used in the NTIA/ITS
HF Propagation Models. This will try to explain what indices to use.
- The SunSpot Number (SSN) used by these HF prediction programs should be what is called
R12 - the Smoothed SunSpot Number.
- NGDC used to have it linked
in this table.
- That was last updated May 15, 1999.
- George Lane says to use:
ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/sunspot.predict
for compatibility with VOACAP.
- SEC also maintains SunSpot data with slightly different numbers under
Solar Cycle Progression.
- For past values, you must use the
Recent Solar Indices table.
- The proper column in this table is Smoothed RI
- For predicted values, you must use the
Predicted Indices table.
- The proper column in this table is SunSpot Number Predicted
- You will notice that the Predicted table is about 6 months behind the current date. That
is because it takes that long for the smoothed SunSpot Number to become permanent.
- I (G. Hand) questioned someone at SEC as to what was the difference between SEC's and NGDC's
sunspot predictions, and here is his response.
- Note: We cannot control the content nor accessibility
of the NOAA web pages.
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