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Last update: Friday, 22-Sep-2023 06:46:58 GMT
SB PROP @ ARL $ARLP038
ARLP038 Propagation DE K7RA
QST DE W1AW
ARRL Propagation Bulletin 38 ARLP038 From Tad Cook, K7RA
Seattle, Washington September 22 2023
To all radio amateurs
"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 is today. 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 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.
More Parker Solar Probe news.
A new video from Dr. Tamitha Skov, WX6SWW:
Send your tips, reports, observations, questions and comments to firstname.lastname@example.org. When reporting observations, don t forget to tell us which mode you were operating.
Also, check this article from September, 2002 QST:
An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation . More good information and tutorials on propagation are at http://k9la.us/
Instructions for starting or ending email distribution of ARRL bulletins are at http://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. NNNN
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