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The K7RA Solar Update


Over the recent reporting week (January 28 through February 3) both sunspot and solar flux averages were down a negligible amount, and geomagnetic numbers were down substantially, compared to the previous seven days.

Average daily sunspot numbers declined from 57.3 to 50.6, while average daily solar flux values went from 106 to 105.4. Average daily planetary A index softened from 11.6 to 7.3, while the mid-latitude A index (measured in Fredericksburg, Virginia) went from 7.6 to 5.6.

The latest predicted solar flux is 125 on February 5-6, 120 on February 7, 115 on February 8, 110 on February 9-11, 105 on February 12-20, 100 on February 21 through March 2, 95 on March 3, 90 on March 4-5, 95 on March 6-8 and 105 on March 9-18.

Predicted mid-latitude A index is 6 on February 5, 5 on February 6, then 8, 18, and 12 on February 7-9, 6 on February 10-11, 5 on February 12-16, then 10, 15, 12 and 10 on February 17-20, 5 on February 21-27, then 8 on February 28-29, 15 and 8 on March 1-2, 5 on March 3-5, then 12, 10 and 8 on March 6-8 and 5 on March 9-15.

OK1MGW predicts geomagnetic activity will be mostly quiet February 5-6, quiet to active February 7-8, quiet to unsettled February 9-10, mostly quiet February 11, quiet February 12-14, quiet to unsettled February 15, quiet to active February 16-18, quiet to unsettled February 19-20, mostly quiet February 21, quiet February 22-25, mostly quiet February 26-28, quiet to active February 29 through March 1, and quiet to unsettled March 2.

During the March 16-18 period when he predicts quiet to active conditions, we may see active to disturbed conditions Match 16-17, although he is uncertain about this.

He says we may see increased solar wind on February 7-8, 16-18 and February 29 through March 1.

Skip Burroughs, KS5KIP, of Capitan, New Mexico sent a query about how to apply some of the data from this bulletin to get a feel for what propagation will be like.

One way to do this is to use a propagation prediction program and do predictions based on your location for various locations and frequencies of interest.

One free program for doing this is W6ELprop, which you can download from K9LA has some more info on running the program here: and here:

Basically what we want to see in the weekly numbers are rising solar flux and sunspot numbers and lower A index, at least ideally.

You could take the average daily sunspot number from the bottom of this bulletin (50.6 in this bulletin) and use that in the program. If we run that for Capitan, New Mexico for this Sunday toward Japan, we see that 40 meters should be good 0600-1500 UTC, with best signals around 0900-1400 UTC. 30 meters seems good 0700-1430 UTC, 20 meters looks rather weak, but possibilities include 2100-0300 UTC and another possible opening at 1500-1600 UTC. 17 meters looks much stronger 2130-0200 UTC, and 15 meters 2200-0030 UTC. 12 meters looks promising 2230-2330 UTC.

From Capitan to Chicago, 15 meters looks possible 1730-2000 UTC, 17 meters looks better 1630-2200 UTC, 20 meters 1500-0000 UTC and 30 meters 1330-0130 UTC. 40 meters looks excellent any time of the day or night, with best signals 0100-1300 UTC and open, but about 13 db lower signals but still open 1730-1930 UTC. 75 meters looks best 0130-1230 UTC.

Vary the date using the same numbers, and you will see seasonal effects on propagation. For instance, the path to Japan on March 22 opens on 17 meters an hour earlier and closes over 2 hours later.

Next week I should have an evaluation copy of ACE-HF, another propagation tool and I hope to review it.

Now that January is over, we can look at our 3-month moving averages of sunspot numbers t check the progression of this solar cycle. This gives us the latest number, centered on December 2015.

We saw the peak centered on February and March 2014, when the three month moving averages were 146.4 and 148.2. The highest single monthly average at the peak of the solar cycle was February 2014, at 174.6.

The latest 3-month average was 55.4 centered on December 2015, which included all of the daily sunspot numbers from November 1, 2015 through January 31 2016.

The 3-month moving averages of sunspot numbers centered on January through December 2015 were 98.2, 78.1, 68.2, 72.4, 77.7, 76.3, 69.1, 67.5, 64.5, 64.6, 58.5 and 55.4. With this moving average you can see a smooth, steady decline in cycle 24.

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 28 through February 3 were 64, 49, 30, 39, 42, 52, and 78, with a mean of 50.6. 10.7 cm flux was 109.9, 106.9, 105.1, 101.2, 100.2, 102.1, and 112.1, with a mean of 105.4. Estimated planetary A indices were 6, 3, 3, 10, 9, 6, and 14, with a mean of 7.3. Estimated mid-latitude A indices were 5, 3, 3, 8, 6, 4, and 10, with a mean of 5.6.



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