XPost: rec.radio.shortwave, rec.radio.info

SB PROP @ ARL $ARLP037
ARLP037 Propagation de K7RA

ZCZC AP37
QST de W1AW
Propagation Forecast Bulletin 37 ARLP037

From Tad Cook, K7RA

Seattle, WA September 27, 2024
To all radio amateurs

SB PROP ARL ARLP037
ARLP037 Propagation de K7RA

Seven sunspot groups emerged this week. The first was on September 19, three
on September 20, one each on September 22 and 23, and the last on September
25.


Average daily sunspot numbers increased from 120 to 137.2, and average daily solar flux shifted from 175.7 to 164.3.


Geomagnetic numbers were much quieter. Average daily planetary A index
changed from 35.7 to 14.3, and middle latitude A index from 23.4 to 10.7.


Predicted solar flux is 180 September 27 to October 1, 190 on October 2-6,
185 on October 7-9, 180 on October 10, 175 on October 11-16, 170 on October 17-18, 165 on October 19, 160 on October 20-23, 165 on October 24-26, then
170 and 175 on October 27-28, 180 on October 29-30, and 190 on October 31 through November 2.


Predicted planetary A index is 5 on September 27-28, 8 on September 29-30, 5
on October 1-4, 10 on October 5-6, 5 on October 7-9, then 10, 20 and 19 on October 10-12, and 5 on October 13-21, 8 on October 22-23, 5 on October
24-31, and 8 on November 1-2.


"Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere
- September 26, 2024 from OK1HH:


"Solar flare activity is generally lower than it was in the first half of September, when M-class solar flares were common and X-class flares also occurred. The last significant M-class flare, including a CME, was observed
on September 22. However, the Earth's magnetic field activity increased on September 25-26, incidentally in good agreement with the forecast.


"Propagation conditions, especially in the shorter half of the shortwave
range, have understandably improved, but not as much as we might have
expected in the run-up to the equinox. This was influenced by a decrease in solar activity (compared to August levels) - and of course an increase in geomagnetic activity.


"Unlike in times relatively recently past, any of us can monitor not only
total solar activity, but also changes in solar wind parameters. Both its
speed and the concentration of free electrons and protons ejected by flares. Changes in the ionosphere follow quickly, but not always in the same way. It
is also always the result of previous developments."


Latest report from Dr. Tamitha Skov, WX6SWW:
https://youtu.be/B9jWbAVEpZw [ https://youtu.be/B9jWbAVEpZw ]

Send your tips, reports, observations, questions and comments to
k7ra@arrl.net [ mailto:k7ra@arrl.net ] . When reporting observations, don't forget to tell us which mode you were operating.


For more information concerning shortwave radio propagation, see www.www.arrl.org/propagation [ http://www.arrl.org/propagation ] and the ARRL Technical Information Service web page at, www.arrl.org/propagation-of-rf-signals [ http://arrl.org/propagation-of-rf-signals ] .

For an explanation of numbers used in this bulletin, see www.arrl.org/the-sun-the-earth-the-ionosphere [ http://arrl.org/the-sun-the-earth-the-ionosphere ] .


An archive of past propagation bulletins is at www.arrl.org/w1aw-bulletins-archive-propagation [ http://arrl.org/w1aw-bulletins-archive-propagation ] .

More good information and tutorials on propagation are at http://k9la.us/ [ http://k9la.us/ ] .


Also, check this QST article:
https://bit.ly/3Rc8Njt [ https://bit.ly/3Rc8Njt ] "Understanding Solar
Indices" from September 2002 QST.


Instructions for starting or ending email subscriptions to ARRL bulletins are at www.arrl.org/bulletins [ http://arrl.org/bulletins ] .


Sunspot numbers for September 19 through 25 2024 were 109, 113, 117, 114,
224, 123, and 160, with a mean of 137.1. 10.7 cm flux was 161.2, 153.8, 158, 162.8, 167.4, 172.4, and 174.2, with a mean of 164.3. Estimated planetary A indices were 20, 7, 6, 5, 13, 17, and 32, with a mean of 14.3. Middle
latitude A Index was 15, 6, 6, 3, 9, 12, and 24, with a mean of 10.7.

NNNN
/EX

ARRL® The National Association for Amateur Radio®
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