Propagation Forecast Bulletin 18 ARLP018
From Tad Cook, K7RA
Seattle, WA May 6, 2022
To all radio amateurs
SB PROP ARL ARLP018
ARLP018 Propagation de K7RA
https://www.spaceweather.com reported on May 4 at 0859 UTC that an M5 solar
flare erupted from sunspot group AR3004, causing a shortwave radio
blackout over the Middle East and Africa.
Please see https://bit.ly/3vKzelk
A recent flare update:
Solar activity was lower this week, even though we could see
sunspots every day.
Average daily sunspot numbers dropped from 109.3 to 68.6, while
average daily solar flux went from 156 to 120.
Average daily geomagnetic indices were only slightly higher, with
average planetary A index changing from 9.1 to 10.7, and middle
latitude A index from 8 to 9.3.
Predicted solar flux looks low for the next month, even dipping
below 100 in early June. In fact, from Wednesday to Thursday the
predicted solar flux for the first week of the forecast dropped
For a comparison, see this week’s ARRL Letter at,
Predicted values are 118 on May 6-8, then 115, 110 and 112 on May
9-11, then 115, 115 and 120 on May 12-14, 125 on May 15-18, 127 on
May 19-20, then 130, 128, 125, and 122 on May 21-24, 118 on May
25-26, then 114 and 110 on May 27-28, 105 on May 29-31, then 102 and
100 on June 1-2, 97 on June 3-5, then 99, 102 and 108 on June 6-8,
then 115 on June 9, 120 on June 10, and 125 on June 11-14.
Predicted planetary A index is 5 on May 6, 8 on May 7-8, 5 on May
9-12, then 8, 10 and 8 on May 13-15, 5 on May 16-19, then 12 and 8
on May 20-21, 5 on May 22-23, 18 on May 24, 15 on May 25-27, then 8,
15 and 8 on May 28-30, then 5 on May 31 through June 8, then 8, 1,
and 8 on June 9-11.
These predictions are from forecasters Housseal and Dethlefsen of
the USAF 557th Weather Wing.
Recent flare activity in the news:
Thanks to KA3JAW for this story:
Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s
Ionosphere from OK1HH:
“We have seen more of large solar flares this year, but it was
usually by night in Europe. On April 30, the first major flare
finally occurred during the day, thanks to which we were able to
observe the ShortWave Fadeout (SWF) in the western part of the Old
World. Solar X-rays caused abnormally high ionization in the
ionospheric D region, where attenuation increased significantly. Our
shortwave receivers fell silent at 1337 UTC.
“The solar flare peaked at 1347 UTC, ending at 1352 UTC. Only then
could the attenuation in the ionospheric D region begin to decline
and signals other than those coming via ground wave gradually
appeared. Solar activity began to rise again mainly due to active
area No. 3004, which emerged on May 2, and grew rapidly.
“Its magnetic structure became more complex with increased energy,
with significant eruptions up to several times a day. In addition,
they were often accompanied by type IV radio noise bursts, which
indicated that the solar plasma cloud had left the Sun. As Group
3004 is now facing approximately toward us, we can expect at least
one of the clouds to hit Earth, causing a disturbance. Perhaps we
will see further improvement in the shortwave propagation
conditions, during the possible positive phase of its development.”
KA3JAW sent this report about signals heard on the 8 meter band:
“On Saturday, April 30, 2022, between 1607-1632 UTC I received
WM2XEJ in Grid Square EM82 calling CQ using digital mode FT8 on the
experimental 8-meter (40 MHz) band via short-haul sporadic-E.
Distance was 670 miles (1078 km), with an azimuth of 220 degrees.
“The 8-meter experimental band is within the worldwide
Industrial-Scientific-Medical (ISM) segment between 40.660 to 40.700
MHz with a 40 kHz bandwidth, center frequency on 40.680.
“Licensed users are Fixed, Mobile and Earth exploration-satellite
“WM2XEJ is an FCC Part 5 Experimental Radio Service station operated
by Tom Mills, WB4JWM in Eatonton, Georgia. Tom is authorized to
operate at 400 watts of Effective Radiated Power (ERP) using CW,
SSB, digital modes FT4, FT8, WSPR, and Q65.
“Tom uses an Icom IC-9100 rig into a vertical loop antenna giving
about 300 watts of ERP.”
Amateur radio has 8 meter allocations in the UK, Slovenia, Denmark,
and South Africa.
Here is a blog devoted to 8 meters:
If you would like to make a comment or have a tip for our readers,
please email the author at, firstname.lastname@example.org .
For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation and the ARRL Technical Information
Service web page 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/.
Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins .
Sunspot numbers for April 28 through May 4, 2022 were 118, 90, 50,
36, 69, 53, and 64, with a mean of 68.6. 10.7 cm flux was 132.2,
123.5, 119.7, 109, 111.9, 113.8, and 130.1, with a mean of 120.
Estimated planetary A indices were 14, 15, 18, 9, 6, 7, and 6, with
a mean of 10.7. Middle latitude A index was 11, 10, 16, 9, 6, 7, and
6, with a mean of 9.3.