Average daily sunspot numbers over our reporting week (February 25 through March 2) were marginally higher than the previous seven days, going from 37.9 to 41.4, while average daily solar flux was down by just one point, to 92.9.

Average planetary A index changed from 10.1 to 5.9 and average mid-latitude A index went from 12.6 to 5.3., so it was a quiet week with stable geomagnetic conditions.

Predicted solar flux from USAF/NOAA for the near term is 100 on March 4-7, 105 on March 8-13, 100 on March 14-15, 95 on March 16-20 and then bottoming out at 90 on March 21-26. Flux values then peak at 115 on March 30-31.

The planetary A index prediction shows 12, 15, 20, 15 and 10 on March 4-8, then 8 on March 9-11, 5 on March 12 and 12 on March 13. The predicted A index then makes a huge jump to 30 on March 14-16. This perhaps is from a recurring coronal hole, because on April 10-12 the A index again goes to 30. Note that in mid-February there were similar numbers on February 17-19 of 38, 34 and 29.

Petr Kolman, OK1MGW, of the Czech Propagation Interest Group (actually they call it the Propagation Interested Group, but I suspect Interest Group is a better translation to standard American English) sent his outlook for geomagnetic conditions. He says to expect quiet to unsettled conditions on March 4, quiet to active March 5-6, quiet to unsettled March 7-8, quiet to active March 9-10, quiet to unsettled March 11-12, quiet to active March 13, active to disturbed March 14-16, quiet to active March 17, mostly quiet March 18-19, quiet on March 20-21, mostly quiet March 22-24, quiet March 25-26, quiet to unsettled March 27, quiet to active March 28-29, and quiet to unsettled March 30.

Petr expects an increase in solar wind on March 5-6, 9-10, 13-16 and 27-29.

Notice that his expected active to disturbed conditions on March 14-16 lines up with the prediction for an A index of 30 on those same dates from USAF/NOAA.

February is done, so let’s examine our 3-month moving average of sunspot numbers.

According to our own data, Cycle 24 peaked with a 3-month moving average of 146.4 and 148.2 centered on February and March of 2014. Four months later the moving average centered on July 2014 was 109.2, and December 2014 was 107.8. January 2015 was 98.2, the first time the average was below 100 since September 2013. July 2015 was 69.1, December 2015 was 55.4, and the latest number centered on January 2016 was 53.5. (The moving average centered on January is an arithmetic average of daily sunspot numbers from December 1, 2015 through February 29, 2016. Adding all sunspot numbers for those days totals 4,868 and divided by 91 days yields an average of 53.4945 or 53.5.

The last time the average was at this level was February 2011, five years ago, when it was 55.7.

The ARRL International SSB DX Contest is this weekend, and it runs from 0000 UTC March 5 through 2359 UTC March 6. See http://www.arrl.org/arrl-dx for details.

Eric Guzman, NP3A, had a comment on N0JK’s note about what a difference a year makes on 10 meters. Eric wrote “I think is not only 10 meters. This February I will complete one year of monthly reports using our Club Skimmer KP3Z data.

“Comparing the 2015 to 2016 tally for the ARRL DX CW Contest, 80 meter activity was down 9 percent, 40 was up 9 percent, 20 meters down 20 percent, 15 meters down 75 percent and 10 meters down 89 percent. I believe this is just the number of callsigns copied, but it was 14,503 on 10 meters last year, and only 1,644 this year.

“Full SH5 reports for both weekends can be found here: http://www.np3a.com/website/index.php/skimmer-sh5

“Huge difference on 15 meters as well. Of course there are other factors that affect these numbers like participation, but in general propagation is the main factor.”

Thanks Eric. Forty meters was the only band with an increased count, and with propagation down on 10, 15 and 20 meters, where else would you go?


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 the download.

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 February 25 through March 2 were 26, 41, 37, 38, 44, 39, and 65, with a mean of 41.4. 10.7 cm flux was 91.7, 89, 90.4, 93.2, 90.9, 96.8, and 98.2, with a mean of 92.9. Estimated planetary A indices were 5, 7, 4, 4, 5, 9, and 7, with a mean of 5.9. Estimated mid-latitude A indices were 6, 5, 3, 4, 4, 8, and 7, with a mean of 5.3.