Compared to the last reporting week, this week (September 1-7) average daily sunspot numbers were down, solar flux increased, and geomagnetic indices were much more active.

Average daily sunspot number declined from 60.1 to 46.4, while average solar flux went from 87.9 to 95.1. Average planetary A index increased from 8 to 26.6, while average mid-latitude A index rose from 6.9 to 18.1.

The daily planetary A index on September 1-4 was 36, 39, 40 and 28. It looks like an echo of the solar wind which caused this activity is expected on September 28 through October 1, when the predicted planetary A index is 35, 38, 40 and 25.

Predicted solar flux is 95 on September 9-10, then 92, 90, and 85 on September 11-13, 80 on September 14-16, 108 on September 17-19, then 110, 105 and 110 on September 20-22, 112 on September 23-24, 108 on September 25, 105 on September 26-27, 100 on September 28, 95 on September 29 through October 1, 98 on October 2-4, 95 on October 5-6, 90 on October 7-8, 95 on October 9, 100 on October 10-11, 105 on October 12, and 108 on October 13-16. After October 16 flux values meander from 105 to 112.

On September 5 predicted solar flux values for September 13 to October 21 got a big boost, a predicted increase ranging from 18-30 points from the September 4 prediction.

Predicted planetary A index is 15 on September 9, 8 on September 10-11, 10 on September 12, 8 on September 13-15, 5 on September 15-16, then 8, 5, 15, 12 and 8 on September 17-21, 5 on September 22-25, then 12, 8, 35, 38 and 40 on September 26-30, then 25, 20 and 12 on October 1-3, 10 on October 4-5, 5 on October 6-9, then 10, 8, 5, 5, 8, 5, 15, 12 and 8 on October 10-18, and 5 on October 19 and beyond.

Petr Kolman, OK1MGW of the Czech Propagation Interest Group predicts the geomagnetic field will be:

Quiet on September 23-24

Mostly quiet on September 9-11, 14-16, 18, 22, October 5

Quiet to unsettled on September 12, 17, 21, 25, 27, October 3-4

Quiet to active on September 13, 19-20, 26, 28-30, October 1-2

Active to disturbed on September (29-30)

Increased solar wind from coronal holes is expected on September 12-13, 17, 19-21, 25-26, 28-30, October 1-2

 Remarks:

- Parenthesis means lower probability of activity enhancement.

Propagation expert Carl Luetzelschwab, K9LA gave a talk (via the internet) to the World Wide Radio Operator’s Foundation on August 23, as reported this week on the ARRL web site: http://bit.ly/2c3yMbZ. Also, note the link in the article to Carl’s presentation to the club, “Solar Topics – Where We’re Headed.” See/hear it at http://bit.ly/2ceGTiE.

Carl notes that some forecasters of space weather have predicted smaller solar cycles in the future. But personally, I would not be so sure. (I’m always searching for something to be positive about, when it relates to future solar activity.) Check out this presentation by Douglas Biesecker, Chair of the Solar Cycle 24 Prediction Panel http://bit.ly/2cz5zkD which does not predict low solar activity extending decades into the future. Note also that Carl predicts a future Cycle 25 at least as strong as Cycle 24.

Carl also mentioned a number I had not heard before. He notes that many solar cycles in the past have been equivalent to Cycle 19, the biggest sunspot cycle experienced by anyone still alive today. He projects back over the past 11,000 years, and with the number he gives, the next grand maximum after Cycle 19 in the late 1950s might be around year 2537. Carl did not predict this; I am just trying to extrapolate from the numbers he mentioned, to get some very rough idea of how uncommon Cycle 19 was.

His numbers show that over the past 11,000 years, 19 notable grand maximums — including Cycle 19 and the cycles around it — and 27 notable grand minimums were recorded. “We’re likely to have more of both grand maximums and grand minimums in the future,” he predicted. But arithmetically estimated from 19 maximums in 11,000 years, that puts the next big one (after Cycle 19) at 521 years from now, maybe in cycle 71.

Finally, we received a note from Dick Ferry, K2KA, of Westford, Massachusetts concerning 6-meter auroral propagation on September 3: “Some notes of last night’s brief AU opening. Got up at 1230am (0430Z) Sep 3, saw AU activity on 6 meters. I heard KL7NO on 50.1056 MHz.  He was very weak, barely copyable, but I did hear him. I didn't call him as he was only audible for a few seconds. K0KP/B, N8PUM/B and VE4VHF/B were loud, but no humans on the band. The beacons were gone in about 10 minutes.”

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 September 1 through 7 were 66, 50, 46, 59, 22, 32, and 50, with a mean of 46.4. 10.7 cm flux was 95.2, 94.6, 99, 97.4, 93.8, 92.4, and 93, with a mean of 95.1. Estimated planetary A indices were 36, 39, 40, 28, 17, 14, and 12, with a mean of 26.6. Estimated mid-latitude A indices were 29, 24, 21, 20, 13, 12, and 8, with a mean of 18.1.