Solar activity reached moderate levels this past week, but has now
returned to, and remains at, lower levels. Region 4248 produced an
M1.1 flare on October 20, which was the largest event of the period.
Region 4261 was numbered this period as it rotated into better
viewing conditions.

Region 4262 was numbered this period as well, splitting it from
Region 4257. Additionally, new spots were noted near N08W00 and
N09E67 but went unnumbered due to a lack of flaring and time of
emergence. No Earth-directed CMEs were observed in available
coronagraph imagery. Solar activity is expected to remain low, with
a chance for isolated M-class flares (R1-R2/minor-moderate).
 
Additional notable activity included a type II radio sweep with an
estimated speed of 2,474 km/s and a type IV radio sweep that began
on October 21. Significant field line movement, appearing to
originate from beyond the northwestern limb, was observed in GOES
SUVI imagery beginning on October 21.  The subsequent coronal mass
ejection (CME) was then first seen on LASCO C2 coronagraph imagery
on October 21. This event has been analyzed as a far-sided
asymmetric halo.
 
Solar wind parameters were mildly enhanced this period due to
negative polarity coronal hole high speed stream (CH HSS)
influences. Solar wind speeds exhibited a decreasing trend from
approximately 600 km/s to under 500 km/s by the period's end. Phi
was predominantly positive while undertaking brief excursions into
the positive solar sector. Mildly enhanced solar wind conditions and
waning negative polarity CH HSS influences were expected to
continue.

Solar activity is expected to be at moderate levels from October 31
to November 15 due to the return of Region 4246. Low levels are
expected to prevail to October 30, and then on November 14 and 15.
Geomagnetic field activity is expected to reach G1-G2
(Minor-Moderate) storm levels on October 28 to 30.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere, October 23, 2025, by F. K. Janda, OK1HH:

"Although it may not seem so at first glance, solar activity is
still at the peak of its 25th cycle. Although the number of sunspot
groups fell to six in mid-October, a week later it had risen to ten.
Few eruptions were observed on the solar disk, or the side of the
Sun facing Earth, including only a few that could be classified as
moderately strong based on the intensity of X-ray emissions.

"However, something is brewing on the far side of the Sun. This is
evidenced by the occurrence of three CMEs, the first on October 21
and the other two on October 22. The increased concentration of
protons with an energy of 10 MeV (and a lower concentration of 100
MeV) in the solar wind confirms that this is significant activity.
To analyze the development of the relevant activity, we will have to
wait until it appears on the eastern limb of the solar disk.

"The geomagnetic field has calmed down in recent days. The next
disturbance is expected around October 28. At first glance, this is
very good news for shortwave propagation conditions during the
weekend of October 25-26, but if geomagnetic activity increases
during these days, it will come as no surprise.

"In fact, with the right timing of the disturbance, it could be
followed by an increase in MUF and an overall improvement. Although
a significant deterioration in propagation conditions is expected
with a relatively high probability only after the aforementioned
disturbance (i.e., around October 29), it may occur earlier."

The Predicted Planetary A Index for October 25 to 31 is 10, 5, 5,
25, 35, 25, and 15, with a mean of 17.1.  Predicted Planetary K
Index is 3, 2, 2, 5, 6, 5, and 4, with a mean of 3.9.  10.7-centimeter flux is 150, 150, 150, 145, 145, 145, and 140, with a mean of 146.4.

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.