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ARRL Propagation Bulletin ARLP021 (2022)

ARLP021 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 21  ARLP021
From Tad Cook, K7RA
Seattle, WA  May 27, 2022
To all radio amateurs 

ARLP021 Propagation de K7RA

Although our Sun is currently peppered with spots, average daily
sunspot number slipped from 134.1 the previous week to 124.7 during
this reporting week, May 19 to 25.

Average daily solar flux was actually a tiny bit higher, rising
hardly at all from 157.3 to 158.8. Solar flux has been in a slow,
steady decline from a peak of 179.9 on May 18.

A new sunspot group emerged on May 19, two more on May 22, another
on May 24 and two more on May 25. But a look at the total sunspot
area, expressed in millionths of a full solar disc, shows it
declining steadily through the week, from 1500 on May 19 down to 870
on May 25.

AR3014 is the biggest sunspot group of the current solar cycle:

There were plenty of solar flares this week, although no significant
disturbances to note.

Here is a movie of a flare appearing on May 20:

Another flare on May 25 at 1824 UTC, emerging from an old dead
sunspot group:

The Thursday prediction from USAF shows average daily solar flux
dropping from 158.8 over the recent week to 114.5 for the following
reporting week, May 26 through June 1. Also, the Thursday projection
for solar flux in the next week was lower than the Wednesday

Predicted solar flux is 120, 115 and 110 on May 27 to 29, 112 on May
30 to June 1, 115 on June 2, 120 on June 3 and 4, 115 on June 5 and
6, then 130, 140 and 150 on June 7 to 9, 155 on June 10 and 11, then
160 and 165 on June 12 and 13, 175 on June 14 and 15, 165 on June 16
to 19, then 163, 132, and 158 on June 20 to 22, 150, 142 and 138 on
June 23 to 25, then 135, 130, 125 and 120 on June 26 to 29, 120 on
June 30 through July 1, and 115 on July 2 and 3.

Predicted planetary A index is 15, 18, 15, 12 and 10 on May 27 to
31, 5 on June 1 to 9, then 8, 14, 12, 14 and 8 on June 10 to 14,
then 12, 14, 12, 14 and 8 on June 15 to 19, 5 on June 20 to 22, then
10, 10 and 8 on June 23 to 25, and 5 on June 26 through July 6.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - May 26, 2022 from OK1HH.

"The current accelerating growth of solar activity is leading to
predictions that the maximum of the current cycle 25 should be
comparable to cycle 19. Solar cycle 19 was the nineteenth solar
cycle since 1755, when extensive recording of sunspot activity
began. Solar cycle 19 lasted 10.5 years, beginning in April 1954 and
ending in October 1964. The maximum smoothed sunspot number observed
during the peak of cycle 19 was 285, in March 1958.

In the last 14 days, the solar flux has not fallen below 130. A
total of 13 M-class solar flares were registered.

The critical frequencies of the ionospheric layer F2 in the same
interval corresponded to the effective sunspot number 72 to 116,
while drops below 100 occurred exclusively after days with slightly
increased geomagnetic activity.

It's already summer in the ionosphere of the Earth's Northern
Hemisphere. This corresponds to lower values of the highest usable
frequencies with the daily occurrence of sporadic layer E. The
optimal frequencies for DX QSOs therefore fell below 20 MHz. With
the exception of routes leading above lower latitudes, where they
tend to be several MHz higher during the day.

In the coming weeks, the activity of the sporadic layer E in the
ionosphere of the northern hemisphere will intensify. Although solar
activity should increase again after June 10, the activity of the
sporadic layer E will have an even more significant effect on the
opening of the shortest shortwave bands."

Recent flare news:

NN4X wrote:

"There was some amazing propagation on Thursday, 5/26 on 12m to Asia
over the north pole. I was called, and worked, in succession:

EX8MLE 1618 UTC  9V1XX 1619 UTC  DS4FWI 1620 UTC  VU2CPL 1627 UTC

Sadly, 6m never opened, but the fun didn't stop with 12m in the

15m was spectacularly open around 0200 UTC on Thursday evening.

The band was literally open ALL OVER THE WORLD."

Steve included a pskreporter map showing spectacular worldwide FT8
coverage for his signal.

From Max White, M0VNG, concerning latitudinal asymmetry in sunspot

Posted to an email list devoted to propagation beacons on Thursday

"Late evening. Only heard one beacon around 0345 UTC:

ZL3TEN, 28.2279 MHz, 579  Path: 7,827 miles

Unbelievable so late at night and signal so strong.

73, Lou  WD5GLO-EM15AH  Oklahoma"

On May 24 I sent this to propagation expert K9LA:

"Over and over recently I do an FT8 test using pskreporter on 10
meters and if no response there, I check 12 meters, usually around
1600 to 1800 UTC.

Every day shows my signals ONLY being received in Florida, the path
about 2500 miles. Often there will be an XE station or two, also at
2500 miles.

But that's it, nothing else. But later in the day there will be a
few stations elsewhere.

The bearing is 103 to 105 deg.

This is consistent, day after day. I am sure Florida has a large ham
population, but cannot for the life of me figure this out.

On 10 meters a half hour ago AG0N in Nebraska reported, 999 miles
away and also a 106 degree bearing, but otherwise see a huge
concentration of Florida stations.

Any idea why this is happening, other than perhaps a large and
enthusiastic concentration of FT8 stations monitoring in Florida?"

Carl replied:

"Tad, your observations remind me of when I've operated on 10m
around solar minimum from the Cayman Islands. Most of the QSOs are
in the vicinity of MN - which is about 2500 miles (4000 km) from ZF.
The openings are very selective in location when there aren't enough
sunspots for shorter distances.

The 2500 mile distance (4000 km) is right at the maximum F2 region
hop length for 12m and 10m. That means the F2 region MUF is the
highest for paths of that length.  Thus your FL and XE paths could
be one F2 region hop. Any shorter paths would need more ionization
to refract the higher elevation angles for those shorter distances.

As for New England, the midpoint of the path would be farther north,
which means a lower MUF.

The Nebraska path might be via sporadic E, as 2000 km is the maximum
hop length for the E region. Could the FL and XE paths be 2 hops via
sporadic E? Perhaps - it'd be nice to have some data, but there
aren't any ionosondes near those paths.

If I had to bet, I'd go with one F2 region hop for FL and XE, and
one Es hop for Nebraska."

On May 25th I replied:

"Attached is an image from pskreporter from this morning on 12
meters, with Florida represented by better conditions with coverage
up the east coast."

Carl responded:

"That PSKreporter image with the densest reports from along the East
Coast suggests that it was one F2 hop, and that the F2 region was
better on May 25 at 1942 UTC than the previous days. The day-to-day
variation of the F2 region certainly explains it well.

It would be interesting to collect data for the entire day - maybe
in 2-hour increments to see the patterns versus time. That may be a
way to distinguish between F2 and Es."

I received a link from IL4LZH for a page showing interesting
analysis of signals received at his station over the past few years:

"Here at 

You can find some data plots that I have collected in recent years.

They are analyzed by ITU zone and hours of days. Horizontally 40 ITU
zone inside ITU zone hours from 00 to 23 vertically day of the month
green intensity linked to intensity of signal."

Carrington event,

Dr. Tamitha Skov on May 22,

This weekend is the CQ World Wide CW WPX contest. You may be sought
after if you have a 2x1 call sign (like my former call, KT7H)
because the first few characters of your call may be unique. See .

For more information concerning shortwave radio propagation, see and the ARRL Technical Information
Service at For an
explanation of numbers used in this bulletin, see

An archive of past propagation bulletins is at More good
information and tutorials on propagation are at

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

Sunspot numbers for May 19 through 25, 2022 were 154, 109, 110, 138,
132, 137, and 93, with a mean of 124.7. 10.7 cm flux was 173.2,
165.5, 166.7, 164.7, 158.2, 146.9, and 136.5, with a mean of 158.8.
Estimated planetary A indices were 10, 12, 10, 11, 5, 4, and 6, with
a mean of 8.3. Middle latitude A index was 10, 12, 9, 11, 6, 3, and
7, with a mean of 8.3.


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