Solar activity remained at low levels this past week with numerous C1
flares from Region 4420, which exhibited growth during the period.
Region 4419 showed minor decay, particularly in its trailing spots,
while producing a lone C1.0 flare. Region 4422 was numbered during
the period but remained inactive. No Earth-directed CMEs were
observed in coronagraph imagery.

Solar activity is expected to continue at low levels, with a slight
chance for isolated M-class activity, through April 24, primarily due
to the flare potential from Region 4420 and limb activity.

Solar wind parameters reflected waning coronal hole high speed stream
(CH HSS) influences. The wind speed maintained an average of 525
km/s, and Phi was predominantly in a negative orientation towards the
Sun.

Region 4419  was the most active region of the period, responsible
for 5 out of the 7 C-class flares observed during the week, including
the largest one: a C4.1. The remainder 2 C-class flares of the period
were a C1.1 from Region 4414 and a C1.6 from Region 4416. Coronal
activity was observed during the week with some filament eruptions
and few CMEs without Earth-directed components.

Spaceweather.com reports the sun has been quiet for weeks. That ended
today with two powerful X-class solar flares. In quick succession,
sunspot 4419 unleashed X2.4 (0107 UT) and X2.5 (0813 UT) explosions.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere, April 23, 2026, by F. K. Janda, OK1HH:

Although solar activity during the first four months of this year was
lower than in the previous two years of the 11-year solar maximum
(2024–2025), this was anything but a continuing decline. Periods of
low solar activity gradually tended to lengthen and were interspersed
with sudden increases in both overall and eruptive activity. This
trend is very clearly evident in the solar flux, which was very low
during the penultimate solar cycle (March 14–21), followed by a
further and longer decline shortly after the beginning of April and
particularly between April 9 and 13.

Moreover, during the long period of low solar activity (April 5–22),
geomagnetic field activity increased (April 18–21), further
diminishing hopes for the usual seasonal improvement in shortwave
propagation conditions. However, two sunspot groups then emerged on
the eastern limb of the solar disk, bringing their total number to
four. Then came Thursday, April 23, with several moderately powerful
solar flares, alternating between the east and west of the solar
disk, preceded by rapid changes in magnetic configuration where the
eruptions were soon observed.

Therefore, in the coming days we will continue to observe increased
solar activity and the potential effects of fast solar wind on Earth.
Shortwave propagation conditions will vary irregularly, while during
the ongoing bursts of intense solar wind, ionospheric attenuation
will increase at higher latitudes.

The Predicted Planetary A Index for April 25 to May 1 is 8, 5, 5, 5,
20, 18, and 12 with a mean of 10.4. The Predicted Planetary K Index
is 3, 2, 2, 2, 5, 5, and 4 with a mean of 3.3. 10.7 centimeter flux
is 115, 120, 125, 125, 125, 125, and 125 with a mean of 122.9.

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.