SB PROP @ ARL $ARLP045
ARLP045 Propagation de K7RA
QST de W1AW
Propagation Forecast Bulletin 45 ARLP045
>From Tad Cook, K7RA
Seattle, WA November 6, 2020
To all radio amateurs
SB PROP ARL ARLP045
ARLP045 Propagation de K7RA
10.7 cm solar flux density was 88.1 on Wednesday, November 4, the
highest since October 14, 2016 when it was 92.8.
The average daily solar flux for that week as reported in this
bulletin was 76.9, and average daily sunspot number was 18.7 (see
https://bit.ly/3oYTDxO), so activity four years ago was similar to
recent activity (in fact those numbers closely match the flux and
SSN in last week's bulletin). But in 2016 Solar Cycle 24 was
declining, reaching a minimum about three years later, in December
The daily solar flux is measured at noon local time (GMT -8 hours)
in Penticton, British Columbia, but there are actually three daily
measurements, at 1800 UTC, 2000 UTC and 2200 UTC.
Solar flux has been steadily increasing since the 2000 UTC reading
on November 2. The three daily readings through November 5 were
81.6, 81.9, 82.9, 82.9, 83.7, 86.9, 88.1, 89, 91.1, 90.7 and 92. But
the daily 2000 UTC reading is always reported as the official number
for the day.
https://www.spaceweather.gc.ca/solarflux/sx-5-flux-en.php is where
you can see all the daily flux readings.
Average daily sunspot number during the current reporting week
(October 29 through November 4) was 21.3, compared to 17 over the
prior seven days. Average daily solar flux was 81.6, compared to
76.9 reported last week.
Average daily planetary A index this week was 6.3, down from 12.3
last week. Average daily mid-latitude A index was 4.9, down from 9.9
Spaceweather.com reported at 0703 UTC on November 3 the new sunspot
group produced a minor solar flare, and a pulse of UV radiation
"briefly ionized Earth's upper atmosphere, causing a low-frequency
radio blackout over the Indian Ocean."
Later another flare occurred at 0022 UTC on November 5, which caused
a brief blackout over Australia and the Pacific Ocean, causing
signals below 10 MHz to fade.
Check https://stereo.gsfc.nasa.gov/beacon/ for a 360-degree view of
the STEREO image, which you can see in its conventional format at,
Predicted solar flux is 88 on November 5-10, 83 on November 11, then
dropping to 75, 74 and 75 on November 12-14, 76 on November 15-21,
75 on November 22-27, 74 on November 28-29, 72 on November 30
through December 5, 74 on December 6-10, 75 on December 11, 76 on
December 12-18, and 75 on December 19.
Predicted planetary A index is 5, 8 and 8 on November 5-7, 5 on
November 8-16, 10, 5, 10 and 15 on November 17-20, 12 on November
21-22, then 8, 10 and 12 on November 23-25, 5 on November 26-27, 10
on November 28, 5 on November 29 through December 13, then 8, 5 and
8 on December 14-16, 12 on December 17, and 10 on December 18-19.
The forecast was from November 4, but unfortunately there was no
updated prediction on November 5. But you can check these daily flux
and geomagnetic predictions updated daily at,
There is a big new sunspot group, AR2781, which Spaceweather.com
reports is the largest so far in new Solar Cycle 25. It should be
geo-effective (facing Earth) over the next ten days.
Geomagnetic activity forecast for the period November 6 to December
2, 2020 from F.K. Janda, OK1HH.
"Geomagnetic field will be:
quiet on: November 6-7, 9-11, December 1-2
quiet to unsettled on: November 8, 12-15, 19, 26-27, 30
quiet to active on: November 16-18, 22-25, (29)
unsettled to active: November 21, (28)
active to disturbed: November 20
"Solar wind will intensify on: November (18-20,) 21-25 (30, December
"Parenthesis means lower probability of activity enhancement."
This weekend is the CW portion of the ARRL Sweepstakes contest,
running from 2100 UTC Saturday until 0259 UTC on Monday. See
http://www.arrl.org/sweepstakes for details.
A cool photo of the WWV antennas in Colorado, and from an unusual
If you would like to make a comment or have a tip for our readers,
For more information concerning radio propagation, see
http://www.arrl.org/propagation and the ARRL Technical Information
Service at http://arrl.org/propagation-of-rf-signals. For an
explanation of numbers used in this bulletin, see
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/.
For customizable propagation charts, visit the VOACAP Online for Ham
Radio website at, http://www.voacap.com/hf .
Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins .
Sunspot numbers for October 29 through November 4, 2020 were 35, 32,
26, 12, 11, 15, and 18, with a mean of 21.3. 10.7 cm flux was 84.6,
79.6, 76.8, 77.3, 81.6, 82.9, and 88.1, with a mean of 81.6.
Estimated planetary A indices were 14, 5, 6, 10, 3, 3, and 3, with a
mean of 6.3. Middle latitude A index was 11, 4, 6, 8, 2, 2, and 1,
with a mean of 4.9.