Solar activity is perking up this week.  Average daily solar flux rose from 85.3 last week to 97.3 this week (September 10-16).

Over the same two weeks, average daily sunspot numbers rose from 37.3 to 66.9.

The latest forecast from USAF/NOAA shows solar flux at 110 on September 18-20, 105 on September 21-22, 100 on September 23, 95 on September 24, 90 on September 25-26, then 85, 80 and 85 on September 27-29, then 90, 95 and 90 on September 30 through October 2, 85 on October 3-6, then 90 and 95 on October 7-8, 100 on October 9-10, 105 on October 11-12, then 100 and 95 on October 13-14, and 90 on October 15-23.

Predicted planetary A index is 8, 12, 16, 8 and 6 on September 18-22, 5 on September 23-24, 10 on September 25, then 5 on September 26-29, 8 and 18 on September 30 through October 1, then 25, 20 and 12 on October 2-3, then 25, 20, 18, and 12 on October 4-7, then 18, 15, 10, 12, 20 and 12 on October 8-13 and 8 on October 14-15.

F.K. Janda, OK1HH, of the Czech Propagation Interest Group (who has been providing weekly forecasts with OK1MGW since 1978) sends along his geomagnetic forecast, which sees quiet to active conditions September 18-19, mostly quiet September 20, quiet on September 21, active to disturbed September 22, quiet to active September 23-24, quiet to unsettled September 25, mostly quiet September 26, quiet September 27-28, mostly quiet September 29, quiet to active September 30 through October 1, quiet to unsettled October 2, quiet to active October 3, active to disturbed October 4-5, quiet to active October 6, quiet to unsettled October 7, active to disturbed October 8, quiet to active October 9, mostly quiet October 10, quiet to active October 11, active to disturbed October 12, quiet to unsettled October 13 and mostly quiet on October 14.

He sees increases in solar wind on September 18, 20-22, 25-28, October 3-5 and 8-9, but is less certain about the September 18 and 25-28 periods.

Cecil Williams, NW8F, of Wheelersburg, Ohio asks “Is this cycle nearing its end and what can be expected this fall/winter for 80 and 160 meters? The bands are starting to have a lot more DX it seems. Yesterday I heard D67GIA on 20 meters (later on 15 meters) and he had a decent signal.”

No, this solar cycle (number 24) is just past the peak, which was in spring 2014. The next solar minimum may be coming around 2019 or 2020.

You can see the predicted sunspot numbers out through the end of 2019 here, in the table on page 13:

http://legacy-www.swpc.noaa.gov/weekly/pdf/prf2088.pdf

While solar activity has been slightly higher this week, Cecil may be noticing a seasonal change in conditions as the autumnal equinox approaches next week on Wednesday, September 23.

If we do a prediction for 20 meters from Cecil’s station to Comoros using W6ELprop, and compare current conditions to conditions on August 1, there is a big difference in the length and quality of the openings, with marked improvement as we approach the equinox.

Also, if solar activity continues to decline, this should be good for 80 and 160 meter conditions.


For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of the numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at http://bit.ly/1VOqf9B and http://bit.ly/1DcpaC5 .

Click on “Download this file” to download the archive and ignore the security warning about file format. Pop-up blockers may suppress download. I’ve had better luck with Firefox than Internet Explorer.

Monthly propagation charts between four USA regions and twelve overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins.

Sunspot numbers for September 10 through 16 were 42, 79, 87, 75, 52, 66, and 67, with a mean of 66.9. 10.7 cm flux was 83.5, 92.8, 99.1, 98.8, 96.5, 101.1, and 109.4, with a mean of 97.3. Estimated planetary A indices were 13, 59, 16, 11, 14, 18, and 12, with a mean of 20.4. Estimated mid-latitude A indices were 10, 36, 13, 8, 10, 17, and 9, with a mean of 14.7.