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ARRL Propagation Bulletin ARLP048 (2023)

ARLP048 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 48  ARLP048
From Tad Cook, K7RA
Seattle, WA  December 1, 2023
To all radio amateurs 

ARLP048 Propagation de K7RA


"Several CMEs are expected to impact Earth over 30 Nov and 01 Dec.
Two CMEs were observed on 27 Nov that were expected to arrive on 30
Nov, followed shortly by a very mild glancing blow from a third.

"One or possibly two halo CMEs were observed on 29 Nov which are
Earth directed.  It is likely all or some of these CMEs will combine
on their trajectory toward Earth, making it difficult to pinpoint an
exact arrival time, however G3-G4 geomagnetic conditions are
possible over this period."

Over the past reporting week, ten new sunspot groups appeared.
Three on November 23, one each day on November 24 to 26, another on
November 28 and three more on November 29.

Solar numbers increased, with average daily sunspot number rising
dramatically from 83.3 to 165.9, doubling the previous week's

Average daily solar flux rose from 146 to 181.5.

Geomagnetic numbers rose only slightly, with planetary A index
changing from 10.1 to 11.6, and middle latitude numbers from 7.3 to

Predicted solar flux is 166 and 162 on December 1 and 2, 158 on
December 3 and 4, then 156, 152, 150 and 140 on December 5 to 8, 145
on December 9 and 10, 140 on December 11 to 16, 150 on December 17,
then 160 on December 18 to 28, then 165, 160 and 150 on December 29
to 31, then 145 on January 1, 2024, 140 on January 2 to 4, and 145
on January 5 and 6.

Predicted planetary A index is 54, 22 and 10 on December 1 to 3, 16
on December 4 and 5, 12 and 8 on December 6 and 7, 5 on December 8
to 11, then 10 and 8 on December 12 and 13, 5 on December 14 to 17,
then 15, 25, 8 and 5 on December 18 and 21, then 20, 10, 10, and 8
on December 22 to 25, and 5 on December 26 to 30, then 10, 16, 12
and 10 on December 31 through January 3, 2024, and 5 on January 4 to

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere December 1 to 7, 2023 from OK1HH.

"A week ago the CW portion of the CQ World Wide DX Contest was held.
Prior to that there were several scenarios of possible developments
during the weekend of November 25 and 26, 2023.  In the end the less
likely scenario was the one that developed.  This was due to a
relatively inconspicuous C-class solar flare observed on November

"However, a detailed analysis of its evolution revealed that it was
preceded by a pre-eruption, which was the first signal that a CME
was likely to follow.

"Further observations from satellites and radio telescopes confirmed
the CME and measured the speed of the particle cloud.  Its
rendezvous with Earth was expected on November 24, which would have
been bad enough for the contest.  However, the particle cloud hit
the Earth a day later.  Therefore shortwave propagation improved on
November 25 (especially in the afternoon UTC, during the positive
phase of the disturbance), whereupon an aggravation occurred on the
following day.

"The maximum of solar cycle 25 is approaching.  CMEs, originating
from more energetic solar flares, or from solar plasma filament
eruptions, are hitting Earth with increasing frequency.

"For example, at the time of this writing, another geomagnetic
disturbance is expected as another CME from the eruption observed on
November 28 is expected to hit Earth on December 1 and 2.

"In the meantime, we are observing a rather large coronal hole in
the southeastern solar disk, which will deflate along its
southwestern quadrant over the next week.

"In particular, we are observing active regions to the east of it.
This neighbourhood will result in further intensification of the
solar wind and variations in geomagnetic field activity over the
next week.  Its predictions do exist, but they will not be

I noticed that OK1HH has a packet radio address.  His address is:


Cycle peak in 2024?

Cycle peak in the next few months?

Predicting cycle peaks.

A new long video 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.

A archive of past propagation bulletins is at propagation .  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 November 23 through 29, 2023 were 176, 184, 179,
169, 159, 130, and 164, with a mean of 83.3.  10.7 cm flux was
194.2, 178, 176.4, 180.2, 187.3, 183.5, and 170.6, with a mean of
146.  Estimated planetary A indices were 7, 7, 38, 10, 7, 7, and 5,
with a mean of 10.1.  Middle latitude A index was 4, 5, 18, 9, 2, 6,
and 9, with a mean of 7.3.


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