Solar activity reached moderate levels early this past week with
several flares. An X1-class flare erupted mid-week, but activity has
slowed down with the majority of the low-level C-class flares. A
coronal mass ejection (CME) was observed on May 27 with a flare from
Region AR4100.

Modelling determined the CME to be well behind Earth's orbit. No
other potentially Earth-directed CMEs were detected in available
coronagraph imagery. M-class flare activity, minor - moderate, is
likely, with a slight chance for X-class flare events, strong or
greater, through May 30.
  
The forecast of Solar and Geomagnetic Activity to June 21, 2025:

Solar activity is likely to reach moderate levels
(R1-R2/Minor-Moderate), with a chance for R3 (Strong), over the next
three days as Region AR4098, the most productive region on the
visible disk, makes its way to the west limb of the Sun. A chance
for M-class X-ray activity (R1-R2) will persist throughout the
outlook period due to multiple regions on the visible as well as
multiple active regions scheduled to return from the far side of the
Sun.

No proton events are expected at geosynchronous orbit.

The Geomagnetic field activity is expected to be at a mostly
elevated level due to anticipated influence from multiple, recurrent
coronal holes. G1 (minor) geomagnetic storms are likely on June
13-14; active conditions are likely over June 2, June 5, June 10 and
11, and June 15 to 17.

Unsettled conditions are likely over June 3 and 4, June 6 and 7, and
June 18 to 21.  Quiet conditions are only expected on June 8 and 9.

On May 30, Spaceweather.com reports on a Super-Fast Solar Wind, and
a 24-hour Geomagnetic Storm.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - May 29, 2025, from F. K, Janda, OK1HH:

"On May 29, geomagnetic activity reached the level of a strong storm
(Kp 7) worldwide, which came as no surprise to those who had been
monitoring the recurring disturbances during the last four solar
rotations, and especially the developments on the Sun over the last
five days or so.

"Solar flares were observed, only occasionally with coronal mass
ejections (CMEs). Although the large coronal hole in the southwest
of the solar disk disappeared, other coronal holes appeared across
the solar disk in the meantime. The largest of these extends from
the southwest to the northeast and has been crossing the central
meridian since May 26. It has negative polarity and is associated
with the arrival of a high-speed stream (up to about 730 km/s). Even
in the coming days, after the current disturbance subsides, mild
active storm conditions (Kp 4) will continue.

"Overall solar activity will increase slightly in the coming days,
and geomagnetically active days will alternate irregularly with
calmer ones. Ionospheric conditions for shortwave propagation will
improve, but at best only to average levels."

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 May 31 to June 6 is 8, 10, 12,
8, 10, 12, and 10, with a mean of 10.  The Predicted Planetary K
Index is 3, 3, 4, 3, 3, 4, and 3, with a mean of 3.3.  Predicted
10.7 centimeter flux is 125, 120, 115, 110, 110, 115, and 120, with
a mean of 116.4.