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The K7RA Solar Update


The weekly averages of daily sunspot numbers and solar flux barely changed at all compared to the previous week.  Average daily sunspot numbers went from 73.4 to 79.6, while average daily solar flux decreased from 110.6 to 109.7.

The weak peak of this solar cycle continues. We are moving toward the fall season, which is always seasonally better than summer for HF propagation. Let’s hope for a rise in solar activity to complement the seasonal change.

The latest prediction from NOAA/USAF for the near term has solar flux at 115 on August 2-3, 110 on August 4-6, then 115, 120 and 115 on August 7-9 105 on August 10-12, 100 on August 13, 105 on August 14-18, 100 on August 19-24, and 125 on August 25. Flux values hit a minimum around 100 on September 3-4, and rise to a peak of 135 on September 11-12.

Expected planetary A index is 8, 12 and 8 on August 2-4, 5 on August 5-8, 8 on August 9-10, 5 on August 11-20, then 10, 15 and 10 on August 21-23, 5 on August 24-26, 10 on August 27, 15 on August 28-31, 8 on September 1, and 5 after September 1.

Petr Kolman, OK1MGW presents a weekly geomagnetic prediction from the Czech Propagation Interest Group.  He predicts active to disturbed conditions for today, August 2, quiet to active August 3, quiet to unsettled August 4, mostly quiet August 5, quiet to unsettled August 6-7, mostly quiet August 8-11, quiet August 12-13, quiet to active August 14-15, quiet to unsettled August 16-18, mostly quiet August 19-20, quiet to active August 21-22, and mostly quiet August 23-24. Petr says that growth in the solar wind may cause remarkable changes to the magnetosphere and ionosphere on August 2-3 and 14-16.

NASA released their monthly solar cycle prediction, and there is no change from last month.  You can read it at

At the beginning of each month we take a look at the latest numbers from our 3-month moving average of daily sunspot numbers. We do not see any upward trend. We see two peaks, one toward the end of 2011 and another smaller peak this spring. In 2011, the 3 month periods centered on October and November had average daily sunspot numbers of 118.8 and 118.6. This spring the 3-month periods centered on April and May had averages at 106.4 each. Could these be the double-peaks of solar activity that some have predicted for this sunspot cycle?

The 3-month moving averages of daily sunspot numbers centered on January through June 2013 were 73.6, 80.7, 85.2, 106.4, 106.4, and 97.5. Just to clarify, the 3-month period centered on June includes sunspot numbers for all of the 92 days from May 1 through July 31. The sum is 8,970. Divide that total by 92, and the result is exactly 97.5.

Jon Pollock, K0ZN, of DeSoto, Kansas reported 17 meter observations in last week’s bulletin ARLP030, and this week has another report.  He wrote, “I won't keep reporting this, but I thought this was again instructive since I am seeing this so frequently lately. On Friday, July 26 I was up late and again decided to give 17 meters a try at Midnight CST. Again 17 meters was very quiet, no signals at all. i.e. "Dead". Except that I heard some weak thunderstorm crashes in the background. My experience has been that often when you hear that, the QRN source is a long way away. I called CQ about five times (400 watts CW into a ground mounted vertical with a large radial system) and VK7CW in Burnie, Tasmania came back (now about 12:15 AM CST) with a nice signal, about S-6. He was running 100 watts to a hexbeam. We ended up having a rag chew, and ours were the only signals either one of us could hear on the band over a 9,380 mile path from Eastern Kansas. Again, 17 meters is more often than not open when it seems dead, often for long haul contacts.”

Rick Lindquist, WW1ME, sent a link to yet another article about the current solar cycle being the weakest in one-hundred years. It also mentions a July meeting of the American Astronomical Society Solar Physics Division, which was in Bozeman, Montana. You can read the article at  The American Astronomical Society promises to have downloadable presentation files from the meeting, but nothing yet.  They will be posted 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

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 July 25 through 31 were 71, 58, 64, 68, 97, 105, and 94, with a mean of 79.6. 10.7 cm flux was 106.9, 109.5, 107.9, 109.4, 112.1, 113.1, and 108.7, with a mean of 109.7. Estimated planetary A indices were 11, 14, 11, 7, 6, 6, and 5, with a mean of 8.6. Estimated mid-latitude A indices were 10, 23, 10, 8, 7, 6, and 5, with a mean of 9.9.



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