Last week this bulletin reported a return of sunspot activity on September 29 after a 16-day absence from September 13-28, but the new activity only lasted six days. As of Thursday night (October 11) we are now at seven days with no sunspots visible.
Average daily sunspot number declined from 9.6 to 1.6, while average daily solar flux rose slightly from 68.4 to 68.9.
Average planetary A index increased from 7.7 to 14.1, while mid-latitude A index rose from 6.1 to 10.3.
Predicted solar flux is 71 on October 12, 70 on October 13-18, 69 on October 19 through November 25.
Predicted planetary A index is 8, 5, 12 and 8 on October 12-15, 5 on October 16-17, 12 on October 18-19, then 14, 8 and 12 on October 20-22, 8 on October 23—25, 10 on October 26, 5 on October 27 through November 2, then 22 and 35 on November 3-4, 15 on November 5-6, then 10, 8, 5, 10 and 8 on November 7-11, 5 on November 12-13, then 10, 25, 14, 8 and 12 on November 14-18, 8 on November 19-21, 10 on November 22 and 5 on November 23-25.
Conditions should continue at marginal levels because of weak solar activity.
I keep checking the weekly Preliminary Report and Forecast from SWPC (see ftp://ftp.swpc.noaa.gov/pub/warehouse/2018/WeeklyPDF/ ) because once a month they update solar cycle predictions for smoothed sunspot number and smoothed 10.7 cm solar flux. For the past several years (at least back to early 2015) the projection ended in December 2019. It is widely believed that this cycle (24) should reach solar minimum in 2020, so I keep checking for projections that go past 2019, but so far nothing new is posted.
You can see the latest projection in a recent bulletin on pages 10-11 at ftp://ftp.swpc.noaa.gov/pub/warehouse/2018/WeeklyPDF/prf2249.pdf. It shows the predicted smoothed sunspot number for October 2018 at 11.
Because the smoothed sunspot number is averaged over a year, this means that about half of the current average is made up of real sunspot numbers averaged over the past 6 months and the other part of the average is made up of predicted sunspot numbers over the next 6 months. So, as you look at the averages, for every month you look back, you see the results of more and more real sunspot numbers.
Note that in July 2018 the projected smoothed sunspot number is only 1. This may change as time goes on and more of actual sunspot numbers are figured into the average.
More detail on smoothed sunspot numbers:
http://www.sidc.be/silso/node/52
http://www.astrosurf.com/luxorion/qsl-ssn-history-voacap.htm
Geomagnetic activity forecast for the period October 12 to November 07, 2018 from F.K. Janda, OK1HH.
Geomagnetic field will be:
Quiet on October 13, 16, 29-31, on November 1
Quiet to unsettled on October 14-15, 17, 27, 31
Quiet to active on October 12, 20, 22-26, on November 2, 7
Unsettled to active on October 18, 21, 28, on November 5-6
Active to disturbed on October 19, on November 3-4
Solar wind will intensify on October 12-13, (14,) 17-20, (27-28,) on November 2-5
Remark:
- Parenthesis means lower probability of activity enhancement.
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 October 4 through 10, 2018 were 11, 0, 0, 0, 0, 0, and 0, with a mean of 1.6. 10.7 cm flux was 67.2, 68.7, 68.6, 69.5, 68.8, 69.5, and 69.8, with a mean of 68.9. Estimated planetary A indices were 4, 9, 6, 24, 21, 17, and 18, with a mean of 14.1. Estimated mid-latitude A indices were 4, 8, 5, 13, 16, 14, and 12, with a mean of 10.3.
