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The K7RA Solar Update


Solar indicators dropped this week, with average daily sunspot numbers at 41.6 from November 26 through December 2, down from 62.7 in the previous seven days.

Average daily solar flux dropped 18 points, from 115.2 to 97.2. A week ago the predicted average daily solar flux for the same period was 111.4, more than 14 points above the actual outcome.

Average daily planetary A index was 9.9, while average daily mid-latitude A index was 6.6, more than double the two figures for the previous week, 4.1 and 3.1 respectively. But there were no days with high geomagnetic activity. The most was on Monday and Tuesday, with planetary A index at 19 and 14 indicating moderately unsettled conditions.

Predicted solar flux is 95 on December 4, 90 on December 5-8, 95 on December 9-10, 105 on December 11, 115 on December 12-13, then 110, 105 and 100 on December 14-16, 105 on December 17-18, 110 on December 19-20, 105 on December 21, and 100 on December 22-26. Following this coming week the lowest predicted solar flux is on just one day, at 95 on December 27, five days after the winter solstice.

Predicted planetary A index is 8 on December 4-5, then 18, 25, 20 and 15 on December 6-9, then 8 on December 10-15, then 10 and 8 on December 16-17, 5 on December 18-23 and 8 on December 24-26. The next period of unsettled to active geomagnetic conditions is December 28, with a predicted planetary A index of 25. The planetary A index doesn’t settle down to 5 again until mid-January.

OK1HH predicts geomagnetic activity will be quiet to unsettled December 4-5, active to disturbed December 6-8, quiet on December 9, quiet to active December 10, mostly quiet December 11, quiet to unsettled December 12-14, quiet to active December 15, mostly quiet December 16, quiet on December 17-23, mostly quiet December 24-25, quiet to active December 26-27, mostly quiet December 28, active to disturbed December 29, and back to quiet again on December 30.

He expects an increase in solar wind on December (5 - 7), 8 - 10, (11 – 12, 16 - 20,) 26 - 27, and (28 - 29). He is less certain about heightened activity on the dates in parenthesis.

Unfortunately, we received no reports on conditions during last weekend’s CQ World-Wide CW DX contest. This weekend is the ARRL 160 meter contest. This is a CW only event, and lasts 42 hours with no time limit from 2200 UTC Friday (today) to 1600 UTC on Sunday, December 4-6.

See for complete details and rules.

With low predicted geomagnetic activity over the weekend, 160 meters should be in good shape for the contest.

Average daily sunspot number for the month of November was 61.9. For August, September and October the monthly averages were 61.7, 72.5, and 59.6.

Our three month moving average of daily sunspot numbers, (September 1 through November 30) was 64.6. For the 3 month periods ending in June through October the averages were 77.7, 76.3, 69.1, 67.5 and 64.5. At the cycle’s peak, for periods ending in March and April of 2014, the 3 month moving averages were 146.4 and 148.2. It’s been a pretty steady decrease since then, with the averages dropping below 100 at the beginning of this year.

Don Anderson, N7EF, of Kent, Washington sends this video about a 2018 space mission all the way to the Sun:

Andrew Gudas, N7TP, of Amargosa Valley, Nevada sends along this story about scary superflares:

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 November 26 through December 2 were 56, 48, 36, 47, 51, 27, and 26, with a mean of 41.6. 10.7 cm flux was 103.9, 98.9, 96.6, 95.5, 95.7, 94.6, and 95.3, with a mean of 97.2. Estimated planetary A indices were 3, 7, 8, 9, 19, 14, and 9, with a mean of 9.9. Estimated mid-latitude A indices were 2, 4, 5, 7, 10, 11, and 7, with a mean of 6.6.



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