\n<\/p>\n
Solar flare activity was at low levels in the past week with
isolated C-class flare activity, according to NOAA\u2019s Space Weather
Prediction Center. The largest flare of the period was a C3.4 on
September 8 from otherwise stable Region 4528. Region 4530 developed
asymmetric penumbra on both its leading and trailing poles while
undergoing consolidation in its intermediate area. New flux
emergence in the intermediate area was observed late in the period.
Region 4521 began to show signs of possible flux emergence and pore
development as it produced three C2-class flares on September 8.
Solar activity is likely to be at low levels due to isolated to
occasional C-class flare activity, with a slight chance for M-class
flares (R1-R2\/Minor-Moderate) through September 11.<\/p>\n
Solar wind parameters have been at or close to nominal levels, but
enhanced solar wind conditions due to positive polarity CH HSS
(coronal hole high speed stream) influences are expected to continue
through September 10. On September 11, a separate additional positive
polarity coronal hole high speed stream is likely to arrive, bringing
a mildly disturbed solar wind environment. Quiet to unsettled levels
in the geomagnetic field are expected to prevail on September 10 and
continue into September 11 as another positive polarity CHHSS becomes
geoeffective.<\/p>\n
The Australian Space Weather Forecasting Centre predicts that
degraded HF propagation conditions on September 9 would begin to
clear up on September 10 and 11, leading to normal or normal-fair HF
propagation through all latitudes as we approach equinoctial
propagation conditions.<\/p>\n
Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s
Ionosphere, September 10, 2026, by F. K. Janda, OK1HH:<\/p>\n
The observed number of sunspot groups ranged from six to seven
starting on September 4, while there were occasional Class C and M
solar flares. Sun emitted two coronal mass ejections (CMEs) toward
Earth, but they missed the planet. Nevertheless, the intensified
solar wind following a geomagnetically quiet period from September 1
to 6 contributed to a noticeable increase in geomagnetic activity,
particularly on September 7\u20138. The positive phase of the disturbance
during the afternoon and especially the evening hours UT on the first
day was interesting and impressive. This was, however, inexorably
followed by a negative phase, which significantly affected shortwave
ionospheric propagation as late as September 10.<\/p>\n
No increase in solar activity is expected in the coming days either.
However, after the erratic and disrupted conditions expected in the
second third of September, a calmer period\u2014with significantly more
favorable shortwave propagation conditions\u2014should follow for the
remainder of the month, particularly around the equinox.<\/p>\n
The latest report from Dr. Tamitha Skov, WX6SWW, can be found at
https:\/\/www.youtube.com\/watch?v=rQgzXKOV2ow.<\/p>\n
The Predicted Planetary A Index for September 11 to September 17 is
5, 5, 5, 15, 12, 10, and 5 with a mean of 8.1. The Predicted
Planetary K Index is 2, 2, 2, 4, 4, 4, and 2 with a mean of 2.9.
10.7 centimeter flux is 108, 105, 102, 105, 105, 105, and 105 with
a mean of 105.0.<\/p>\n
For more information concerning shortwave radio propagation, see<\/span>
http:\/\/www.arrl.org\/propagation\u00a0<\/span><\/span>and the ARRL Technical Information<\/span>
Service web page at,\u00a0<\/span><\/span><\/span>http:\/\/arrl.org\/propagation-of-rf-signals. For<\/span>
an explanation of numbers used in this bulletin, see<\/span>
http:\/\/arrl.org\/the-sun-the-earth-the-ionosphere\u00a0<\/span><\/span>. Information and<\/span>
tutorials on propagation can be found at,\u00a0<\/span><\/span><\/span>http:\/\/k9la.us\/\u00a0<\/span><\/span>.<\/span><\/p>\n