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ARRL Propagation Bulletin ARLP042 (2023)

ARLP042 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 42  ARLP042
From Tad Cook, K7RA
Seattle, WA  October 20, 2023
To all radio amateurs 

ARLP042 Propagation de K7RA

Sunspot activity dropped dramatically this week, with only two new
sunspot groups emerging, on October 14 and 16.

Compared to last week, the average daily sunspot number slipped from
144.1 to 89.4, and average daily solar flux from 159.1 to 145.1.

Average daily planetary A index changed from 7.6 to 6.4, and average
daily middle latitude A index from 8.3 to 5.

Predicted solar flux is 128 and 130 October 20-21, 132 on October
22-23, 134 on October 24-25, 136 on October 26, 145 on October
27-28, 150 on October 29 through November 5, 140 on November 6-9,
135 on November 10-11, 145 and 140 on November 12-13, 135 on
November 14-15, then 140 on November 16-18, 135 and 140 on November
19-20, 145 on November 21-24, and 150 through the end of the month.

Predicted planetary A index is 22, 14, 12, 10 and 8 on October
20-24, 5 on October 25-26, 8 on October 27-30, 10 and 12 on October
31 through November 1, 5 on November 2-8, 12 and 8 on November 9-10,
5 on November 11-12, 12 on November 13-14, then 10 and 8 on November
15-16, 5 on November 17-22, and 8 on November 23-26.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - October 19, 2023 from OK1HH:
"In the last ten days, the number of sunspot groups has dropped from
ten to three. At the same time the solar flux has dropped
significantly - from 166 to 135. The last two slightly larger solar
flares were observed on 16 October. The larger of the two occurred
in AR3467. The magnetic filament associated with it exploded and
blew a CME into space.

"According to NASA's models, while it didn't head directly for
Earth, it still likely hit it on October 18 (the original estimate
was that it would happen a day later). Which, while not enough to
cause a geomagnetic storm, was enough to reach an 'unsettled' state.

"This was followed by an erratic MUF from 18 October and then a
decline on 19 October. These lines are written at a time when short
periods of G1 (Minor) geomagnetic storms are not yet ruled out on 19
October, with a possible duration into the first half of 20 October

"A return of larger sunspots and a rise in solar flux towards 150
can be expected by the end of the month."

Regarding 10 meter comments by K7SS in last week's Propagation
Forecast bulletin, Angel Santana, WP3GW of Trujillo-Alto, Puerto
Rico responded, "I second Dan's, K7SS comments on getting on the air
even if you are a Tech on 10 meters.

"I can attest that the band is in good shape: Can contact European
stations with ease even if my antenna is pointing to the US and when
it is 2pm local can still contact them when they are at their local
8-10 pm.

"My score in contests recently reflect more QSOs on 10 meters and
now that we are in contest season it is a great opportunity to get
on the air and see how many countries you can work.

"You can also check and hear SSTV signals on 28.680 MHz as of late
confirming that the band is truly live. And of course, the FM
(29-29.8 MHz) segment."

Dr. Julio Medina, NP3CW wrote:

"Sending some information of activity in 6M band since May to
October 2023.

"Been copying stations from Japan, China, Africa, and many others
such as Philippines on FT8 early in the morning from 1200-1400 UTC
in FT8 in the 6m band."

Jon, N0JK wrote on October 6:

"The 6 meter sporadic-E - linking to TEP (trans equatorial
propagation) openings usually occur in the afternoon. But there was
a late evening Es -- TEP opening on October 6.

"Earlier in the afternoon October 6 I had some weak TEP from South
America to Kansas.  It faded out around 0030 UTC. Then some
sporadic-E took place. Sporadic-E is rare in October, the only month
with less Es is March. That itself is noteworthy, and I logged
stations in Arizona and northern Mexico starting at 0100 UTC October
7 on 6 meter FT8. Then at 0133 UTC I began seeing a FT8 trace at
2,500 Hz. Then it decoded, and was Dale, CE2SV (FF47) sending a
report to W0SZ in Colorado. When they finished, I called CE2SV.
After a couple of calls Dale came back and we completed a contact at
0136 UTC. His signal varied from -10 dB to -17 dB.

"What is remarkable is I was operating from home using just an attic
dipole for an antenna. I also decoded CE3SOC and XQ3MCC. N0LL in
EM09 also worked some South American stations. This was 'evening'
TEP, which typically has a shorter range than afternoon TEP. The
evening TEP signals usually have a distinctive 'TEP flutter' sound
and sometimes don't decode with FT8.  Q65 can be a better digital
mode for evening TEP.

"I saw on the ON4KST 6 meter chat page N9PGG in North Carolina
worked FK8HA and VK4 stations. This was a sporadic-E link (on the
same Es I had to the south) out to the South Pacific.

"On another note -- stations in Central America, the Caribbean and
northern South America have been making 6 meter Long Path contacts
with east Asia and Malaysia from 1200 - 1600 UTC the last couple of

"6 meter long path is best with high solar flux and low geomagnetic

"2023-10-07 15:16 9Z4Y (FK90HM) 50.313.0 FT8 YB0MZI (OI33JQ) LoTW eQSL 18626 km
"2023-10-07 15:00 9Z4Y (FK90HM) 50.313.0 FT8 YB0SAS (OI33JS) LoTW eQSL 18623 km
"2023-10-07 14:54 9Z4Y (FK90HM) 50.313.0 FT8 YB0COU (OI33IU) LoTW eQSL 18611 km
"2023-10-07 14:52 JA6GNL (PM53GO) 50.310.0 FT8 PJ4MM (FK52VE) LoTW 14545 km


"2023-10-07 14:38 PJ4MM (FK52VE) 50.313.0 FT8 4W/JH2EUV (PI21) LoTW 18502 km +12"

A video about predicting Solar Flares (Helioseismology):

A video about a Class X2 flare:

A video about a Cannibal CME:

A report about Solar Cycle history:
The latest report from Dr. Tamitha Skov, WX6SWW:

Send your tips, reports, observations, questions and comments to When reporting observations, don't forget to tell us
which mode you were operating.

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

Also, check this article from September, 2002 QST:

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

Sunspot numbers for October 12 through 18, 2023 were 126, 91, 100,
92, 106, 57, and 54, with a mean of 89.4. 10.7 cm flux was 157.1,
149, 148.2, 144.6, 144, 137.3, and 135.3, with a mean of 145.1.
Estimated planetary A indices were 4, 13, 8, 4, 4, 3, and 9, with a
mean of 6.4. Middle latitude A index was 3, 11, 6, 2, 3, 2, and 8,
with a mean of 5.


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