(C) ARRL Letter
This story was originally published by ARRL Letter and is unaltered.
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The ARRL Solar Report [1]
[]
Date: 2025-09
Spaceweather.com for September 5 reports that a total lunar eclipse
occurs on September 7th. However, it will not be visible in the
Americas.
Solar activity will likely continue at moderate levels with isolated
M-class flares through September 6 due to the combined flare
potential of Regions AR4197 and AR4207. Probabilities decrease to
just a chance for M-class flares on September 7 as AR4197 moves
beyond the western limb.
An enhanced solar wind regime is anticipated to continue into
September 6 due to a positive polarity coronal hole high speed
stream.
On September 7, High Speed Stream activity combined with the arrival
of the September 4th CME is likely to cause further G1 (Minor)
storming levels with a chance for G2 (Moderate).
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere, September 4, 2025, by F. K. Janda, OK1HH:
"As soon as we begin to think that we are starting to understand
what is happening on the Sun and in its vicinity (where we and Earth
are located), Mother Nature shows us that it is not that simple. A
small example: while we were observing the extensive active region
4197 on the Sun, an eruption occurred in another, much smaller and
less conspicuous region, AR4199, which had a key influence on the
events of the following days. It happened on the evening of
Saturday, August 30, very close to the solar equator and the central
meridian, so it was directed towards Earth.
"The forecasts of further developments from all forecasting centers
were identical: the CME would arrive at Earth on September 1 in the
late afternoon to evening hours and cause a G2-class magnetic storm,
accompanied by auroras. And so, it happened.
"As predicted, the geomagnetic disturbance continued on September 2.
This was followed by a relatively rapid calm, and by September 4,
the state of the Earth's magnetosphere and ionosphere began to
approach what we are used to at the end of summer and beginning of
autumn - in other words, there was a noticeable improvement in the
conditions for ionospheric shortwave propagation.
"In further developments, the Earth will be affected by another
surge of solar wind on September 6. But this should come as no
surprise, as it is a regularly recurring passage of the Earth
through a stream of intensified solar wind linked to active areas on
the Sun. The entire system, together with the Sun, rotates once
every approximately 27 days. Therefore, predictions of the onset of
disturbances are relatively reliable."
The latest report from Dr. Tamitha Skov, WX6SWW, can be found at:
https://www.youtube.com/watch?v=XxbAzht2Eq0 .
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.
The predicted Planetary A Index for September 6 to 12 is 8, 12, 12,
12, 10, 5, and 5, with a mean of 9.1 The predicted Planetary K
Index is 3, 4, 4, 4, 4, 2, and 2, with a mean of 3.3. 10.7
centimeter flux is 175, 160, 140, 130, 125, 125, and 120, with a
mean of 139.3.
[END]
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[1] Url:
https://www.arrl.org/news/the-arrl-solar-report-29
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