QST de W1AW  
Propagation Forecast Bulletin 39  ARLP039
>From Tad Cook, K7RA
Seattle, WA  September 25, 2020
To all radio amateurs 

SB PROP ARL ARLP039
ARLP039 Propagation de K7RA

Until September 23, we saw 32 consecutive days with no sunspots.
Then we saw new sunspot group AR2773 which has a magnetic signature
indicating it is part of new Solar Cycle 25.

Spaceweather.com noted it was a weak one, and may not
persist for long. The daily sunspot number for September 23 was 13,
indicating three sunspots visible in that group. But the next day
that sunspot was gone.

Average daily solar flux rose from 69.2 to 71.1 this week (September
17-23). Geomagnetic indicators were about the same, with average
daily planetary A index declining from 5.3 to 5.1.

Predicted solar flux for the following 45 days on Wednesday,
September 23 was 73 on September 24 through October 1, and 70 on
October 2 through November 2.

The next day that forecast was revised to a predicted solar flux of
70 on every day until November 8. But on Thursday, September 24 the
solar flux was 73.6, closely matching the previous day's forecast.

Predicted planetary A index is 15, 12, 25 and 15 on September 25-28,
8 on September 29-30, 5 on October 1-10, 10 on October 11, 5 on
October 12-19, then 10, 12, 16, 28, 18 and 10 on October 20-25, then
5 on October 26 through November 6, 10 on November 7 and back to 5
on November 8.

Geomagnetic activity forecast for the period September 25 to October
20, 2020 from F.K. Janda, OK1HH.

'Geomagnetic field will be:
quiet on: October 6-7 
quiet to unsettled on: October 5, 8-9, 13-16, 18 
quiet to active on: September 30, October 1-2, (3-4, 10, 12, 17,) 19 
unsettled to active: September 25-26, 28-29, (October 11, 20) 
active to disturbed: (September 27)

'Solar wind will intensify on: September (27-28,) 29-30, October 1,
13-14, (15, 21,) 22.

'- Parenthesis means lower probability of activity enhancement.'

Note the OK1HH forecast sees active to disturbed conditions on
September 27, which matches our (actually NOAA and USAF) A index
prediction of 25 on that date. Note this disturbance returns about
30 days later with A index of 28 on October 23.

A great article on tracking sunspot cycles can be found at:
https://bit.ly/33Pifza .

Ken, N4SO on the Alabama Gulf Coast reports that he hears three 15
meter beacons daily on 21.150 MHz, LU4AA in Argentina, OA4B in Peru,
and YV5B in Venezuela. These are part of the NCDXF beacon network,
and he rarely hears the 1 watt transmission. At the other power
levels they are S3-S4.

See https://www.ncdxf.org/beacon/beaconlocations.html .

Several days ago, a new weekly Space Weather video from Dr. Tamitha
Skov, WX6SWW:

https://youtu.be/sitciVFVsfM

If you would like to make a comment or have a tip for our readers,
email the author at, [email protected] .

For more information concerning radio propagation, see
www.arrl.org/propagation and the ARRL Technical Information
Service web page at, at arrl.org/propagation-of-rf-signals.
For an explanation of numbers used in this bulletin, see
arrl.org/the-sun-the-earth-the-ionosphere.

An archive of past propagation bulletins is at
arrl.org/w1aw-bulletins-archive-propagation. More good
information and tutorials on propagation are at k9la.us/.

Instructions for starting or ending email distribution of ARRL
bulletins are at arrl.org/bulletins.

Sunspot numbers for September 17 through 23, 2020 were 0, 0, 0, 0,
0, 0, and 13, with a mean of 1.9. 10.7 cm flux was 69.7, 69.9, 70.6,
70.2, 71.3, 72.4, and 73.3, with a mean of 71.1. Estimated planetary
A indices were 4, 5, 3, 4, 3, 6, and 11, with a mean of 5.1. Middle
latitude A index was 5, 4, 4, 4, 3, 5, and 10, with a mean of 5.