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ARRL Propagation Bulletin ARLP044 (2021)

ARLP044 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 44  ARLP044
From Tad Cook, K7RA
Seattle, WA  October 29, 2021
To all radio amateurs 

ARLP044 Propagation de K7RA

Sunspot activity was up this week, with the average daily sunspot
number increasing by nearly five-fold from 11.3 to 54.9. Average
daily solar flux rose from 78.6 to 95.7. Currently our Sun is
peppered with spots:

A new sunspot group appeared on October 22, another on October 24,
two more on October 25, and another on October 26.

The sunspot number peaked on Thursday, October 28 at 96, and daily
solar flux peaked on the same day at 111.7.

Geomagnetic indicators were nice and quiet, but don’t expect that
to last. Average daily planetary A index went from 8.4 to 4.4 and
average daily middle latitude A index declined from 5.4 to 3.6.

Predicted solar flux looks quite promising, at 113 on October 29,
114 on October 30 through November 1, 110 and 105 on November 2-3,
then 100 on November 4-5, 86 on November 6-7, 85 on November 8-9, 83
on November 10, 82 on November 11-15, 85 on November 16-20, 94 on
November 21, 95 on November 22-23, 96 on November 24, 95 on November
25-29, then 92, 90, and 88 on November 30 through December 2, and 86
on December 3-4.

Predicted planetary A index is 5 on October 29, then 40, 35 and 12
on October 30 through November 1, 5 on November 2-5, then 12, 10 and
8 on November 6-8, 5 on November 9-14, then 10 and 8 on November
15-16, 5 on November 17-22, 8 on November 23-24, 10 on November
25-26, 5 on November 27-28, 8 on November 29, then 5 on November 30
through December 2, then 12, 10 and 8 on December 3-5. reported on Thursday, "A strong G3-class
geomagnetic storm is possible on October 30 when the CME from
yesterday's X-flare is expected to hit Earth's magnetic field." This
is why the predicted planetary A index on October 30-31 is 40 and

At 0129 UTC on October 29 the Australian Space Forecast Centre
issued this geomagnetic disturbance warning:

"(Sunspot) - AR2887 produced X1.0 flare at 28/1535 UTC, which
triggered a halo CME. The CME is expected to arrive at Earth in the
first half of UTC day 30 October. As a result, the geomagnetic
conditions are expected to reach major storm levels with a chance of
severe storm periods. The global Kp index may reach 7 (G3 storms).
On the local night of 30 October (and maybe 31 October), aurora may
be visible from Tasmania and the southern mainland coastal areas.
FROM 30-31 OCTOBER 2021."

This weekend is the CQ World Wide SSB DX Contest, which should be
affected by the increased geomagnetic activity. The CW weekend is
November 27-28. ARRL November CW Sweepstakes is next weekend,
November 6-8.

Geomagnetic activity forecast for the period October 29 to November
23, 2021 from F.K. Janda, OK1HH.

"Geomagnetic field will be:
quiet on: November 4-5, 18-19,
quiet to unsettled on: October 31, November 9, 12-13, 17, 20, 22,
quiet to active on: October 29, November 1-3, 10-11, 21, 23,
unsettled to active on: October 30, November 6-8, 14, 16,
Active to disturbed: November (15),

"Solar wind will intensify on October 30-31, November 1, (8,) 9-10,
(11,) 16-17.

- Parenthesis means lower probability of activity enhancement."

Darrell, AA7FV sent this:

He sent plots of 17 meter WSPR reports on October 28, which he noted
show the obvious effect of a CME from 1520-1550 UTC.

You really should check out his page on, and which give fascinating details of his
activities, and background in astrophysics.

Don't miss Dr. Tamitha Skov, WX6SWW, and her latest video:

From Mike May WB8VLC Salem, Oregon.

"QSOs on upper HF bands For the end of October until 10-27, only the
interesting QSOs are listed as there are just too many others from
17 to 10 meters to include.

"Note this interesting QSO on 15 meters AM, 2021-10-24 16:40 CT1EHI
15m 21.430 AM IM67aa Portugal.

"This was an AM QSO and amazing as signals were solid both ways on

"D4F on 10 SSB was the first real strong African region signal heard
in a long time here on 10 meters and a welcome QSO.

"HD8R has been the big DXpedition this week with big signals on 10
to 17 meters.

"2021-10-27  0129 HD8R 17m  18.080    CW   EI49kd Galapagos Island       
2021-10-26   1540 HD8R 10m  28.024    CW   EI49kd Galapagos Islands      
2021-10-26   1536 HD8R 12m  24.950    SSB  EI49kd Galapagos Islands
2021-10-26   0151 HD8R 15m  21.024    CW   EI49kd Galapagos Islands      
2021-10-24   2227 E51JD 10m 28.420    SSB  BG08ct South Cook Islands     
2021-10-24   1917 VE8WD/M 15m 21.320  SSB  Canada

"A nice QSO with a ham in Yellowknife running 100 watts mobile, he
was over 59 for 2 hours after our QSO."

A Canadian view on solar risks to the power grid:

More on this week's space weather:

In a message titled "Good propagation these days," Angel Santana,
WP3GW reported from Puerto Rico on October 26:

"Yesterday at about 1730 UTC heard M5JON on 28.505 MHz which was a
surprise since it has been a long time since I heard an English
station on 10m. Did QSO with a 5-7 report to this side.

"Today contacted HD8R on 24.950 MHz split 5 up at 1851 UTC.

"I suppose and hope that the CQ WW SSB this weekend is why I am
hearing much activity on all bands."

Small portion of a message from Frank Donovan, W3LPL:

"Propagation crossing low and mid latitudes is likely to be normal
until likely CME arrival early to mid-day Saturday, then mostly
below normal until at least mid-day Sunday.

"We are in the geomagnetically active autumn equinox season through
late October with about twice as many geomagnetically active days
compared to December, January, June and July caused by the
interplanetary magnetic field (IMF) more frequently persisting in a
southward orientation (-Bz).

"Geomagnetic disturbances caused by coronal hole high speed stream
effects are likely to remain mostly brief, minor and somewhat less
frequent through at least late 2021. The southward oriented (-Bz)
component of the interplanetary magnetic field (IMF) plays a crucial
but unpredictable role in triggering all geomagnetic storms.

"Brief minor to moderate geomagnetic storms may be gradually
triggered when the IMF persists in a southward orientation (-Bz)
with enhanced IMF field strength for several hours coincident with
the effects of an Earth directed coronal hole high speed stream.

"More frequent, longer duration, minor to severe geomagnetic storms
may be triggered suddenly and unpredictably when the IMF persists in
a southward orientation (-Bz) with enhanced IMF field strength for
several hours or more coincident with the effects of an Earth
directed fast CME.

"Mid-latitude northern hemisphere sunset is 56 minutes earlier and
daylength is 90 minutes shorter than it was on September 22nd.

"Daytime ionization and residual nighttime ionization in the far
northern polar region is rapidly declining due to steadily
increasing polar night effects."

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

For more information concerning shortwave radio propagation, see and the ARRL Technical Information
Service web page 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 October 21 through 27, 2021 were 11, 28, 32, 46,
81, 95, and 91, with a mean of 54.9. 10.7 cm flux was 81.9, 86.9,
86.8, 93.2, 100.6, 109.3, and 110.9, with a mean of 95.7. Estimated
planetary A indices were 7, 4, 3, 4, 5, 5, and 3, with a mean of
4.4. Middle latitude A index was 9, 3, 2, 2, 4, 3, and 2, with a
mean of 3.6.


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