With sunspot numbers up and solar flux decreasing, we saw ten new
sunspot groups this week; two on September 6, three on September 7,
two on September 8, one on September 9, and two on September 11.

Average daily sunspot numbers increased from 155.3 to 178.4, while
average daily solar flux declined from 230.3 to 223.7.

Geomagnetic indicators were quiet, with average daily planetary A
index dropping from 14 to 7.9 and middle latitude numbers from 12.7
to 11.7.

The solar flux forecast calls for 10.7 cm numbers at 210 on
September 13-14, 205 on September 15-20, then 225 and 220 on
September 21-22, then 225 on September 23-24, then 230, 235, 230 and
225 on September 25-28, and 240 on September 29-30, then 240, 245
and 230 on October 1-3, 220 on October 4-5, 225 on October 6-7, 220
on October 8-9, 225 on October 10-11, 220 and 215 on October 12-13,
210 on October 14-15, then back up to 240 at the end of the month.

Predicted planetary A index is 35 and 25 on September 13-14, then 15
on September 15-16, then 12, 15, 12 and 12 on September 17-20, 5 on
September 21-25, then 25, 25, 15 and 10 on September 26-29, then 5
on September 30 through October 4, 10 on October 5-6, then 30, 22
and 8 on October 7-9, 5 on October 10-13, 8 on October 14-15, and 5
on October 16-22, then 25 on October 23-24.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - September 11, 2024 from OK1HH:

"The solar wind speed, as measured in geostationary orbit, increased
in two jumps on 12 September - first shortly after midnight UTC from
360 km/s to 430 km/s, then to 520 km/s after 0818 UTC. Meanwhile,
the polarity of the longitudinal (north-south) component of the IMF
(Bz) was negative. The consequence was a significant deterioration
of shortwave propagation conditions.

"The development continued on 12 September as the X1.3 solar flare
was detected at 0943 UTC. The source was a new AR turning into view
off the southeast limb (former AR 3792, whose high activity during
the parade on the Sun's far side was well known thanks to
helioseismological observations).

"However, the strong (G3) Geomagnetic Storm followed, while
threshold was reached at 14:43 UTC. Values of critical frequencies
f0F2 in the mid-latitudes of the northern hemisphere of the earth
were 2 MHz lower compared to the previous days. Now it can be
expected geomagnetic disturbance around September 14 (possible
arrival of particles from the September 11 CME). We may wait until
September 18 for quiet days."

WP3GW wrote:

"After a 4 month hiatus, just began again on FT8. I have noted that
the SFI has been more than 200, and have worked European stations at
about 2200 UTC, three hours after propagation normally closes to the
Caribbean.

"And have seen signals late night and in mornings before the Sun
comes up in 10 meters, making it a twenty plus hours open band. Have
made 7 new countries on FT8 in almost 3 weeks.

"Hope these conditions keep good for this contest season.

"Cheers, Angel Santana WP3GW."

Jeff, N8II wrote:

"There have been somewhat limited openings to Europe on 10 meters
for about 2 weeks. On Monday September 2 I worked several Southern
EU and several UK stations, some with good signals. Today, the 8th
was exceptionally good. Not only was the 10 meter band open to all
but possibly NE Europe, but stations in the Middle East were S9 to
S9+20 dB. On SSB I worked A42K, Oman, and 4K6FO, Azerbaijan. Also,
UA9CTT, Asiatic Russia was S9+20 dB and UN4L, Kazakhstan was peaking S8 all of them working the All Asia Contest. I called CQ with the
majority of my callers from the UK all with good signals, many over
S9. The only somewhat weak Brit was a mobile running 5W who was
peaking S5. OH6TS, Finland answered my CQ, and I heard SM5CAK,
Sweden over S9. I was also called by Hungary and Romania. It was
like the middle of October on a good day, very surprising 2 weeks
before the equinox. All of my QSOs were between 1400-1520Z. I also
worked JE6RFM on 15M SSB during that time and heard a JA5 about S7.
There was an Indonesian also on 15M working the Asian contest who
was S9+.

"The Summer has been frustrating with very limited activity except
in contests above 20M. 20M was open through most of the night to
Europe throughout the June-August period.

"The sporadic-E was poor this year, fewer openings and mostly single
hop. Every day 10M was open to Central and South America. Around the
middle of August, we started getting daily openings to the West
Coast. Since then, most days were open to AF and OC. Hawaii has been
loud on several occasions including the NAQP Phone test 2nd weekend
of August and was also briefly loud during the Hawaii QP last
weekend of August.

"Today September 12 there was a good F2 opening to EU; I worked two
R4s (next to Asia), several SP, DL, I, HB9, F.  YL3BF called and was
about S4-6. The UK was not part of the opening. One of the Germans
was running 15W to a 5M long indoor wire and was peaking S9!"

The latest from Dr. Tamitha Skov, WX6SWW, Space Weather Woman:

https://youtu.be/RHphr4iloHs

Impressive sunspots:

https://bit.ly/3zjgI8o

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.

For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation and the ARRL Technical Information
Service web page at, http://arrl.org/propagation-of-rf-signals . For
an explanation of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere .

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/ .

Also, check this:

https://bit.ly/3Rc8Njt "Understanding Solar Indices" from September
2002 QST.

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

Sunspot numbers for September 5 through 11 2024 were 167, 188, 179,
176, 213, 147, and 179, with a mean of 178.4. 10.7 cm flux was
240.7, 248.9, 221.7, 227.6, 214.8, 205.2, and 207, with a mean of
223.7. Estimated planetary A indices were 7, 8, 7, 9, 9, 7, and 8,
with a mean of 7.9. Middle latitude A Index was 8, 8, 9, 19, 9, 7,
and 18, with a mean of 11.1.