Sunspots disappeared again, since August 28. Average daily sunspot number dropped from 17.7 (during the prior week) to 0, (naturally).

Average daily solar flux declined from 70.6 to 67.8. Geomagnetic indicators quieted, with average daily planetary A index changing from 19.9 to 6.3, and mid-latitude A index going from 13.4 to 5.9.

Predicted solar flux is 68 on September 7-14, 75 on September 15-17, 72 on September 18-22, 70 on September 23, 68 on September 24 through October 1, 70 on October 2-6, 72 on October 7, 70 on October 8-9, 75 on October 10-14, 72 on October 15-19, 70 on October 20 and 68 on October 21.

Predicted  planetary A index is 12, 10, 5 and 5 on September 7-10, 20, 15 and 12 on September 11-13, 12 on September 13, 10 on September 14-15, then 15 and 10 on September 16-17, 5 on September 18-21, then 12 and 8 on September 22-23, 5 on September 24-29, 8 on September 30, 5 on October 1-3, then 8, 12, and 8, on October 4-6, then 5, 18 and 15 on October 7-9, 12 on October 10-11, then 10, 15 and 10 on October 12-14, 5 on October 15-18, then 12, 8 and 5 on October 19-21.

When might sunspots return? In recent periods such as this when the sun has been blank for days or weeks, I’ve referenced predicted solar flux values and assumed that relatively higher flux values may indicate when we may see the return of sunspots. But this has often led to disappointment.

Looking at the latest forecast (from ftp://ftp.swpc.noaa.gov/pub/forecasts/45DF/ ) it would seem that September 15-17 (when predicted solar flux is 75) and October 10-14 (the same) are likely times to see sunspots again, or at least more likely than days with lower solar flux predictions. We’ll see.

In each case when an expected sunspot return did not appear, the solar flux forecast changed in advance of the predicted enhanced period.

OK1HH Geomagnetic activity forecast for the period September 07 until October 03, 2018

Geomagnetic field will be:

Quiet on September 9, 17

Quiet to unsettled on September 10, 18-20, 25-28

Quiet to active on September 8, 13-15, 24, October 2

Unsettled to active on September 7, 12, 16, 21, 29-30, October 1

Active to disturbed on September 11, 22-23

Solar wind will intensify on September (10-11,) 14-17, (21,) 22-24, (25), October 1

Remarks:

- Parenthesis means lower probability of activity enhancement.

- Reliability of predictions remains low, of course.

F. K. Janda, OK1HH

(from Czech Propagation Interested Group compiling this geomagnetic activity weekly forecasts since 1978).

Frank Donovan, W3LPL, of Glenwood, Maryland wrote on August 31: “The Solar-Terrestrial Centre of Excellence (STCE) reports that last weekend's reverse polarity sunspot group 2720 belongs to current Solar Cycle 24.

“Because of its reversed polarity, some websites claimed sunspot group 2720 was possibly one of the first groups of new Cycle 25. This is simply not true, in view of its very low eight-degree latitude.

“The next Cycle 25 sunspot groups should have both reversed magnetic polarity and much higher heliographic latitude, typically 20 to 40 degrees from the equator.

“Only two tiny short-lived numbered sunspot groups are currently assigned to new Cycle 25, sunspot group 2620 in December 2016 and 2694 in January 2018.  While both tiny sunspots were assigned to Cycle 25, there is some uncertainty about which sunspot cycle they belong to. A few additional sunspot groups belong to Cycle 25, but they were so tiny and very short-lived that they did not get an assigned sunspot number.

“During each solar cycle, about 3-percent of all active regions have reversed polarity but do not belong to the previous or next solar cycle. This percentage varies somewhat from one solar cycle to the next. With 2000 to 3000 sunspot groups per solar cycle, this means that every cycle has a few dozen reverse polarity sunspots that belong to the ongoing sunspot cycle despite their reverse polarity.

See the full STCE story at: www.stce.be/newsletter/pdf/2018/STCEnews20180831.pdf

This STCE news item provides more details on these numbered and unnumbered Cycle 25 regions and how solar magnetograms are used to detect opposite polarity sunspots: www.stce.be/news/422/welcome.html“

Readers might check the W3LPL page on QRZ.com for impressive photos of his antennas, including this one: https://bit.ly/2MR1ZYL

Here is the latest from Dr. Skov, September 4: https://youtu.be/GRjrIQYVZ6A

Ran across this, from the end of August: https://youtu.be/qtc2oqeSKoo

For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of 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 August 30 through September 5, 2018 were 0, 0, 0, 0, 0, 0, and 0, with a mean of 0. 10.7 cm flux was 68.3, 67.5, 68.3, 67.7, 68.1, 67.5, and 67.5, with a mean of 67.8. Estimated planetary A indices were 4, 5, 5, 5, 5, 9, and 11, with a mean of 6.3. Estimated mid-latitude A indices were 5, 4, 5, 5, 4, 9, and 9, with a mean of 5.9.