08/01/2025
Spaceweather.com reports solar activity was at low levels with only minor
C-class flares observed. Region 4154 produced a C1.4 flare on 31 July. Region
4153 contributed the majority of the flares, including a C1.3 flare, a C1.5/Sf
flare, and a C1.6 flare on 31 July. Both of these regions remained mostly
unchanged during the period. Region 4166 exhibited growth during the period
yet remained mostly inactive. Newly numbered Region 4167 exhibited growth
during the period and produced a C1.9/Sf flare. The remaining regions were
stable or in decay.
Solar activity is expected to be low with a chance for M-class flares,
Minor-Moderate, through 03 August.
Solar wind parameters are expected to continue a waning trend on 01 August as
the negative polarity CH HSS moves from its geoeffective location. An
additional disturbance cannot be ruled out for 02 August due to the 30 July CME
event mentioned in the previous discussion. Aside from the possible CME
influence, conditions are expected to remain at mostly background levels
through 03 August.
Quiet conditions, with isolated unsettled periods, are expected to prevail on
01 August as CH HSS effects gradually wane. Quiet to unsettled levels are
expected on 02 to 03 August, with a slight chance for an isolated active period
on 02 August, due to the possible July CME passage.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere for
July 31, 2025 by F. K. Janda, OK1HH:
We are most likely still in the period of the maximum of 11-year solar activity
cycle No. 25. Its peak was preliminarily recorded in the fall of 2024, but
this year's course was very unusual, while its response in the ionosphere was
unexpected, especially in May and June. Solar activity should continue to
decline slowly this year, with a more rapid decline expected starting in 2026.
Therefore, there is still hope for favorable shortwave propagation conditions
this fall, especially in the shorter part of the range (say, at frequencies
above 20 MHz).
Last week, only relatively small sunspot groups were observed on the Sun, with
no major flares. This was accompanied by smaller fluctuations in the speed of
the solar wind and, therefore, a calmer geomagnetic field. Although the summer
season in the northern hemisphere of the Earth is not favorable for
long-distance shortwave propagation, it was still an improvement over previous
months.
There should be fewer sunspot groups on the far side of the Sun. But it seems
that those that will soon appear will be larger than those we are currently
observing.
Solar ultraviolet and X-ray radiation, together with the solar wind, are the
main causes of changes in the Earth's ionosphere, but they are not the only
ones. The ionosphere also reacts to processes taking place below it. These
include gravitational waves (formed at the interface between air masses of
different densities, for example in meteorological fronts) and infrasound
caused by earthquakes and typhoons. Scientific research into these phenomena
is still in its infancy, and although records of changes in the ionosphere
following the earthquake on the east coast of Kamchatka (M8.8, Tue 29 July
2025, 23:24:51 UTC) are available, for DX signal hunters this is still more of
a curiosity.
The latest solar report from Dr. Tamitha Skov, WX6SWW, can be found on YouTube
at:
https://www.youtube.com/watch?v=-XM4kZ-vvRk[1]
The Predicted Planetary A Index for August 2 to 8 is 5, 5, 12, 8, 5, 20, and
15, with a mean of 10. Predicted Planetary K Index is 2, 2, 4, 3, 2, 5, and 4,
with a mean of 3.1. 10.7 centimeter flux is 140, 150, 155, 155, 155, 155, and
160, with a mean of 152.9.
For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation[2] and the ARRL Technical Information Service
web page at, http://arrl.org/propagation-of-rf-signals[3]. For an explanation
of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere[4] . Information and tutorials
on propagation can be found at, http://k9la.us/[5] .
Also, check "Understanding Solar Indices" from September 2002 QST.
https://bit.ly/3Rc8Njt[6]
[1] https://www.youtube.com/watch?v=-XM4kZ-vvRk
[2] http://www.arrl.org/propagation
[3] http://arrl.org/propagation-of-rf-signals
[4] http://arrl.org/the-sun-the-earth-the-ionosphere
[5] http://k9la.us/
[6] https://bit.ly/3Rc8Njt
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