Solar activity, which has been at low levels, has returned to
moderate levels. Region AR4232 produced the largest event of the
period, an impulsive M3.6 flare (R1-minor) on October 1, 2025.

An associated Coronal Mass Ejection (CME) was observed in subsequent
SOHO LASCO/C2 coronagraph imagery that began on September 29.
Analysis and modelling of the ejecta is ongoing.

Newly numbered Region AR4237 remained relatively quiet as it
developed. Region AR4263 also produced an R1 event with an M1.0/Sf
flare near the end of the reporting period.
 
It is important to note that, after careful assessment of recent
magnetograph imagery, a spot previously associated to region AR4239
is now considered part of the AR4230, explaining its reported size
increase. A new region appeared but remained unnumbered until
further observation.
 
With multiple regions continuing to exhibit growth, flare activity
is likely to remain at moderate levels (R1-R2/minor-moderate) with a
slight chance for an X-class flare (R3-strong) through October 30.
 
Weak enhancements in the solar wind environment, that began
September 29, are likely to continue as influence from a negative
polarity Coronal Hole High Speed Stream (CH HSS) persists.

The CH HSS influences on the solar wind conditions near Earth are
expected to persist through October 5, as the planet continues to be
embedded at the CH associated co-rotating interactive region (CIR).
A recurrent negative CH was observed rotating into the East limb of
the visible solar disk during the period, but no impact is expected
from it in the upcoming days.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere, October 2, 2025, by F. K. Janda, OK1HH:

"During September, a relatively large number of sunspot groups were
observed on the solar disk, but there were almost no energetically
significant eruptions. It seemed to be the calm before the storm.
The question was what would cause the storm and how the disturbance
would develop. Important factors were: the proximity of the Autumn
Equinox and the configuration of areas on the solar disk.

"The following phenomena were key to further developments:
- The Russell-McPherron effect, in which the magnetic field lines of
  the Sun and Earth can connect around the equinox.
- The source of the intensified solar wind heading towards Earth.

"The second condition was also met - we observed coronal holes No.
83 and 84 on the solar disk near active regions No. 4230 and 4238,
with the space between them being close enough to the central
meridian.

"The disturbance began with a so-called positive phase on the
afternoon of September 29 UTC, while the critical frequencies in the
F2 ionospheric layer initially rose for several hours. In the
following days, the solar wind speed gradually increased to an
impressive 800 km/s. The intensity of the geomagnetic disturbance
reached grade G3 (three-hour K indices rose to 6 to 7).

"The return of the ionosphere to normal conditions will be slow, as
solar activity is expected to gradually decline in the first half of
October. In addition, after a slight lull, another disturbance can
be expected around October 7, and even after that, the situation
will not be very calm."

The latest report from Dr. Tamitha Skov, WX6SWW, can be found on
YouTube at:  https://www.youtube.com/watch?v=a7mWOPWe0NA .

The NOAA Space Weather Prediction Center has a webpage that
discusses the current solar cycle progression:
https://www.swpc.noaa.gov/products/solar-cycle-progression .

The Predicted Planetary A Index for October 4 to 10 is 8, 8, 8, 5,
5, 5, and 5, with a mean of 6.3.  The Predicted Planetary K Index is
3, 3, 3, 2, 2, 2, and 2, with a mean of 2.4.  10.7 centimeter flux
is 170, 165, 165, 165, 155, 155, and 155, with a mean of 161.4.

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.