QST de W1AW  
Propagation Forecast Bulletin 38  ARLP038
>From Tad Cook, K7RA
Seattle, WA  September 22, 2023
To all radio amateurs 

SB PROP ARL ARLP038
ARLP038 Propagation de K7RA

ASWFC GEOMAGNETIC DISTURBANCE WARNING ISSUED AT 0249UTC on 22
SEPTEMBER 2023 BY THE AUSTRALIAN SPACE WEATHER FORECASTING CENTRE:

'Solar wind streams from a pair of coronal holes are expected to
mildly increase geomagnetic activity at times during the interval
late 22-Sep to 24-Sep.

'INCREASED GEOMAGNETIC ACTIVITY EXPECTED FROM 22-24 SEPTEMBER 2023.'

Nine new sunspot groups appeared this week, but the averages were
lower.

A new sunspot group appeared every day from September 15-17, four
more on September 18, and one each day on September 19-20.

On Thursday, the start of the next reporting week two more sunspot
groups appeared.

Average daily sunspot numbers declined from 138.1 to 118.4, while
average daily solar flux went from 159.9 to 149.3.

The Autumnal Equinox in the Northern Hemisphere occurs on Saturday,
September 23 at 2:50 AM EDT, or 0650z.  The change in seasons has
been evident recently with improving propagation on 10 and 12
meters.

A fast moving CME hit Earth on September 18, sparking dramatic
displays of aurora across the northern tier of North America and in
Europe as far south as France.

Alaska's college A index was 49 and 61 on September 18-19, while the
planetary A index was 30 and 49.

Predicted solar flux is 162, 162 and 165 on September 22-24, 160 on
September 25-28, 135 on September 29-30, then 130, 135, 130 and 135
on October 1-4, 140 on October 5-6, 135 on October 7-8, then 140,
145 and 145 on October 9-11, then 150, 150, 155 and 150 on October
12-15, and 155, 150, 145 and 145 on October 16-19, then 150, 150 and
145 on October 20-22, 140 on October 23-24, 135 on October 25-27,
then 130, 135, 130 and 135 on October 28-31.

Predicted planetary A index is 15 on September 22, 22 on September
23-24, then 12 and 8 on September 25-26, 5 on September 27-28, 12
and 8 on September 29-30, 5 October 1-11, 8 on October 12, then 5 on
October 13-19, 12 on October 20, 5 on October 21-24, then 8, 12 and
8 on October 25-27, then 5 on October 28 into the first week of
November.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - September 21, 2023 from OK1HH:
 
'Although the site https://solarham.net/ launched on March 15, 2006,
created and still maintained solely by Kevin,VE3EN, is primarily
intended for amateur radio users, it is also very well regarded by
professional astronomers. In addition to information about the Sun,
it contains everything needed to understand the causes of changes in
the ionosphere, and also provides an overview and forecast of the
Earth's magnetic field activity. On Thursday, September 21, we read:
'Solar activity is predicted to remain at low (C-Flares) to moderate
(M-Flares) levels during the next 24 hours. AR-3435 is considered
the most likely region to produce a moderate to strong solar flare.'

'The information can be supplemented by saying that the level of
solar activity has been rising in recent days, and this rise was
accompanied by an increase in solar wind speed from 400 km/s to over
600 km/s between 18-20 September. In particular, the solar wind
proton influx increased significantly on 18 September; moreover, a
geomagnetic disturbance with intensity G2 (Moderate) to G3 (Strong)
took place on 18-19 September.

'The Earth's ionosphere responded to these events with a significant
decrease in MUF, especially since 18 September. Shortwave conditions
were above average for the last time on 10-12 September, including a
positive phase of the disturbance on the latter day. Around the
equinox we usually expect improvement, but now it was the opposite
as a result of disturbances.

'As another very good source of information, I can particularly
recommend the Space Weather Monitor
(https://www.ionosonde.iap-kborn.de/actuellz.htm), as it also
contains the most important data on the Earth's ionosphere.'

>From reader David Moore, on Parker Solar Probe:

https://bit.ly/3ELWC5E

More Parker Solar Probe news:

https://bit.ly/3EOVEpl

A new video from Dr. Tamitha Skov, WX6SWW:

https://youtu.be/pU6i_2FVR2g

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

Also, check this article from September, 2002 QST:

https://bit.ly/3Rc8Njt

An archive of past propagation bulletins is at
arrl.org/w1aw-bulletins-archive-propagation . More good
information and tutorials on propagation are at k9la.us/ .

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

Sunspot numbers for September 14 through 20, 2023 were 110, 96, 88,
94, 139, 143, and 159, with a mean of 118.4.  10.7 cm flux was
145.2, 139.1, 140.4, 144.6, 154.5, 166.1, and 155.5, with a mean of
149.3. Estimated planetary A indices were 18, 7, 7, 16, 30, 49, and
16, with a mean of 20.4. Middle latitude A index was 13, 7, 5, 14,
21, 38, and 15, with a mean of 18.1.