Recent solar activity took a healthy jump this week, with the average daily sunspot number increasing nearly 48 points to 126.9, a positive change of 60 percent compared to the previous week. Average daily solar flux was up 16.4 points to 126.5.

The daily sunspot number rose to 148 on October 15, then 166 on October 17, the highest it’s been since May 15-17 when it was 186, 212 and 198.

Average planetary A index was unchanged, at 8.1. The high latitude college A index indicated active geomagnetic conditions on October 14-15, when it was 31 and 27.

The latest prediction shows solar flux at 135, 130 and 120 on October 18-20, 115 on October 21-23, 110 on October 24-25, 100 on October 26-29, 105 on October 30-31, 100 on November 1-2, 110 on November 3-4, 115 on November 5, 120 on November 6-7, and 125 on November 8-12.

Predicted planetary A index is 8 on October 18, 5 on October 19-20, 12 and 10 on October 21-22, 5 on October 23 through November 10, 12 on November 11, 5 on November 12-16 and 8 on November 17-19.

F.K. Janda, OK1HH, sent his geomagnetic forecast for this week, and it predicts quiet to unsettled conditions October 18, quiet on October 19-20, mostly quiet October 21, quiet to unsettled October 22, quiet October 23-24, mostly quiet October 25-26, quiet to unsettled October 27, quiet to active October 28-29, quiet October 30 through November 3, quiet to unsettled November 4, quiet to active November 5, quiet to active November 6, mostly quiet November 7-8, and quiet to unsettled November 9.

Two weeks ago we offered links to spreadsheets I’ve been maintaining which show the recent history of the NOAA/USAF 45 day forecast for solar flux and planetary A index. The recent forecasts are online at http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html.

You can download my planetary A index sheet at http://snurl.com/280h74f. No password needed this time. It is interesting to check recent forecast trends, such as when projections for future activity trend up or down, and you can see this clearly when you peruse the spreadsheet. Note how there were projections over the last 3-7 weeks showing predicted solar flux values for some periods at 90 or 95. The most recent predictions show a stronger outlook.

Randy Crews, W7TJ, sent this report on October 17: “Last Weekend 10 and 12 meters were the best I have heard all Fall. The Solar Flux rising out of the mid nineties doldrums was a big help. Looks as if we are going to enter a period of reasonably high solar activity, (Solar flux at 100-125) coupled with a long period of quiet geomagnetic conditions and low solar wind, in addition to the seasonal improvements we have in October. The aforementioned coupled with all the DXpedition activity and the upcoming CQ WW SSB Contest, the bands should be hot! I am making the most of 10 and 12 meter propagation, as I don't think propagation on those bands will be there a year from now. (Our solar flux will be pressed to average over 117 this Month. A year ago October's average was 123. I like the old Farm quote: ‘Make Hay While The Sun Shines’.”

That’s right, Randy, flux values were a little stronger a year ago. In bulletins 40-44 from 2012, the weekly averages of solar flux were 128.7, 104.9, 129.2, 143.9 and 116.9. It is interesting though that sunspot numbers are higher now. The average sunspot number over this past week was 126.9, but sunspot number averages from those same 2012 bulletins referenced above for solar flux were 73, 51.7, 97, 95.3 and 58.4.

Jon Jones, N0JK, the QST columnist who writes “The World Above 50 MHz” wrote on October 11 from EM28 in Kansas in a message titled “F2 on 6 meters October 9,” “I heard LW3EX on 50.100 MHz CW weak via afternoon F2/TEP on Oct. 9 ~ 2040 UTC. Walt and other Argentinean stations were much louder about 3 grids south of me (EM28) in Oklahoma (EM25) and Texas. The geomagnetic field was active at the time.”


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/.

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 October 10 through 16 were 138, 115, 106, 125, 136, 148, and 120, with a mean of 126.9. 10.7 cm flux was 120.7, 129, 127.9, 129.3, 125, 125.3, and 128.1, with a mean of 126.5. Estimated planetary A indices were 9, 5, 5, 2, 13, 14, and 9, with a mean of 8.1. Estimated mid-latitude A indices were 7, 3, 3, 2, 10, 14, and 9, with a mean of 6.9.