Solar flare activity is expected to remain at very low levels, with a
chance for isolated C-class flares through September 19, according to
NOAA’s Space Weather Prediction Center (SWPC). Solar wind speed was
steady near 530 km/s, and negative polarity CH HSS (coronal hole
high-speed stream) effects are anticipated to persist through September
18, with additional enhancements likely today due to flanking
influences from CMEs (coronal mass ejections) that departed the Sun on
September 13 and 14. Geomagnetic activity is expected to reach active to
G1 (minor) storm levels today due to combined CH and CME influences.
Unsettled to active conditions are likely on September 18-19 as
enhancements wane.
The Australian Space Weather Forecasting Centre reports that there are
currently three numbered sunspot regions on the solar disk, and that all
three are stable. No flares are expected over the next several days. The
global HF propagation forecast for middle latitudes is normal to fair
today, followed by normal propagation in the days that follow.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s
Ionosphere, September 17, 2026, by F. K. Janda, OK1HH:
On the solar disc, we observe not only a small number of sunspot groups.
These groups are also relatively small and their magnetic structure is
fairly simple. As a result, eruptive activity – including coronal mass
ejections – is low. Although these phenomena do occur from time to time,
they have had no impact on Earth recently. It is mainly the streams of
high-speed solar wind that, upon entering the Earth’s atmosphere, cause
an increase in geomagnetic activity and can therefore be predicted more
accurately.
An increase in solar activity is not expected in the foreseeable
future. The current slightly higher geomagnetic activity should be
followed by a period of calm. The next period of higher geomagnetic
activity is not expected until around the equinox; during that time,
conditions for shortwave propagation through the ionosphere should be
above average, although – due to low solar activity – this will not
apply to the shortest shortwave bands.
The latest report from Dr. Tamitha Skov, WX6SWW, can be found at
https://www.youtube.com/watch?v=wdaQau3mlnk
The Predicted Planetary A Index for September 18 to September 23 is 10,
5, 5, 5, 4, and 4 with a mean of 5.5. The Predicted Planetary K Index
is 3, 2, 2, 2, 2, and 2 with a mean of 2.2. 10.7 centimeter flux is
90, 90, 95, 100, 110, and 105 with a mean of 98.3.
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 . Information and
tutorials on propagation can be found at, http://k9la.us/ .
Also, check this:
https://bit.ly/3Rc8Njt
“Understanding Solar Indices” from September 2002 QST.