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The K7RA Solar Update


Trends over the past week were just the way we like them, with average daily sunspot numbers and solar flux increasing, and geomagnetic indices lower, compared to the previous seven days.

Why do we like these numbers? When solar flux and sunspot numbers are higher, this increases the likelihood that there will be openings on HF. Lower geomagnetic indices suggest lower absorption.

Average daily sunspot numbers rose from 41 to 55.7, and average daily solar flux increased from 98.2 to 106.5. Average daily planetary A index declined from 16.6 to 11.1, while average daily mid-latitude A index went from 10.6 to 8.4.

These comparisons are for the January 7-13 period against the previous seven days.

Predicted solar flux is 105 on January 15, 110 on January 16-18, 105 on January 19-21, 100 on January 22, 105 on January 23-26, 110 on January 27-28, 105 on January 29-31, 110 on February 1-7, then 108, 105 and 100 on February 8-10, 105 on February 11-14, 100 on February 15-18 and 105 on February 19-22.

Predicted planetary A index is 5 on January 15-21, 15 on January 22, 10 on January 23, 5 on January 24-27, then 18, 12 and 8 on January 28-30, 5 on January 31 through February 1, then 15, 12 and 8 on February 2-4, 5 on February 5-6, then 6, 15, 12 and 8 on February 7-10, 6 on February 11-13, 5 on February 14-16, 8 on February 17 and 15 on February 18.

F.K. Janda, OK1HH, of the Czech Propagation Interest Group predicts quiet to unsettled geomagnetic conditions on January 15, quiet to active January 16, quiet to unsettled January 17, mostly quiet January 18, quiet to active January 19-20, mostly quiet January 21, quiet to active January 22, mostly quiet January 23-24, quiet on January 25, quiet to unsettled January 26, active to disturbed January 27, quiet to active January 28, quiet on January 29-31, quiet to active on February 1-2, quiet to unsettled February 3, quiet on February 4-5, mostly quiet February 6-7, active to disturbed February 8 and quiet to active February 9.

There are a couple of articles about propagation in the February 2016 issue of QST. Check out “Radio Wave Propagation: How Waves Attenuate With Distance” by Kai Siwiak, KE4PT on page 37, and “Make the Most of Ten Meters” by Steve Ford, WB8IMY on page 83.

Sorry, no reader reports this week.

Have you tried the online version of the VOACAP propagation prediction program? It’s easy to use, and quite versatile. You can drag the endpoints of any path around the map, and the polar display to the right of the map gives you the hour-by-hour outlook for each band. VOACAP uses the predicted smoothed sunspot number for the month to make the predictions, and that number is already incorporated in the predictions here. Check it out at

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of the numbers used in this bulletin, see An archive of past propagation bulletins is at More good information and tutorials on propagation are at

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at and .

Click on “Download this file” to download the archive, and ignore the security warning about file format. Pop-up blockers may suppress the download.

Monthly propagation charts between four USA regions and twelve overseas locations are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for January 7 through 13 were 57, 80, 84, 73, 41, 29, and 26, with a mean of 55.7. 10.7 cm flux was 103.4, 108.5, 107, 108.9, 108, 105.5, and 104.1, with a mean of 106.5. Estimated planetary A indices were 14, 8, 6, 7, 14, 15, and 14, with a mean of 11.1. Estimated mid-latitude A indices were 11, 6, 5, 7, 9, 10, and 11, with a mean of 8.4.




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