04/03/2026

Solar activity has been at low levels with only C-class flares
produced by Regions 4401, 4405, and 4409. There were 9 numbered
active regions on the solar disk, with 4409 showing the most
significant growth during the period and producing the largest flares
on April 1. A new region emerged but it has not yet been numbered.
ÿ
Multiple filaments erupted during the day on April 1, producing
coronal mass ejections (CMEs) observed in coronagraph imagery, but
their propagation modeling did not suggest impacts to Earth. The
exceptions are the ejecta first observed at GONG H-alpha images on
April 1.
ÿ
Solar activity is likely to reach moderate (R1/R2-minor/moderate)
levels, with a slight chance for X-class (R3-strong) flares through
April 4, due primarily to the flare potential of Regions 4404, 4405
and 4409.
ÿ
Solar wind parameters were near nominal levels with solar wind speed
averaging around 440 km/s.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere,ÿ April 2, 2026, by F. K. Janda, OK1HH:

The increase in overall solar activity during the third ten-day
period of March-albeit with a slight delay-led to a gradual rise in
MUF values, extending into the first days of April. An increase in
solar flare activity did not occur until April 30, beginning with a
flare at 0319 UT with an X-ray intensity of X1.4, which lasted a long
time and was accompanied by a CME. Since a large coronal hole No. 36
was located nearby, a significant increase in geomagnetic activity
was expected. This did not occur until April 2, but already during
several preceding active intervals, we could observe the effects of electromagnetic wave scattering on ionospheric inhomogeneities,
clearly visible even on ionograms.

Active region NOAA 4405, located 27 degrees south of the solar
equator, has been clearly visible for a week as the largest on the
solar disk and appears to be stable. On April 3, it passes the
central meridian, and its proximity to coronal hole No. 36 is a
potential source of intensified solar wind. It also indicates higher geomagnetic activity (at G2 level since April 2). This proximity will
likely be the cause of increased geomagnetic activity during the
first ten days of April. Consequently, this will lead to irregular
shortwave propagation conditions and more frequent drops in the MUF.

The next increase in solar activity will likely occur in the last
third of April. Daily MUF values will rise again, and at the same
time, a sporadic E layer will begin to appear occasionally in
mid-latitudes. Although it will not yet have a significant impact on
shortwave propagation, it will occasionally cause interesting DX
openings on the shortest shortwave bands.

The Predicted Planetary A Index for April 4 to April 10 is 22, 10,
15, 8, 7, 25, and 40 with a mean of 18.1. The Predicted Planetary K
Index is 5, 3, 4, 3, 2, 5, and 6 with a mean of 4. 145, 145, 135,
125, 118, 120, and 110 with a mean of 128.2

For more information concerning shortwave radio propagation, see http://www.arrl.org/propagation[1]ÿand the ARRL Technical Information
Service web page at,ÿhttp://arrl.org/propagation-of-rf-signals[2]. For
an explanation of numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere[3]ÿ. Information and
tutorials on propagation can be found at,ÿhttp://k9la.us/[4]ÿ.

Also, check this:

https://bit.ly/3Rc8Njt[5]

"Understanding Solar Indices" from September 2002ÿQST.


[1] http://www.arrl.org/propagation
[2] http://arrl.org/propagation-of-rf-signals
[3] http://arrl.org/the-sun-the-earth-the-ionosphere
[4] http://k9la.us/
[5] https://bit.ly/3Rc8Njt
---
þ Synchronet þ Whiskey Lover's Amateur Radio BBS

04/10/2026

Solar activity remained at low levels this week. Most of the C-class activity came from either Region 4414 or Region 4409, which has developed a delta spot in its intermediary area. All remaining spots were either stable or in slight decay, with Region 4406 rotating over the west limb by the end of the reporting period.
ÿ
Coronal activity was observed in CCOR-1, LASCO and STEREO available imagery during the period. Of the four eruptions, one was far-sided, one was too narrow plus too far north of the ecliptic to have any Earth-directed component, and two had the potential for Earth-directed components. The first was associated with a C2.4 flare from Region 4414 while there was no clear source for the second. Modeling indicates these eruptions will pass behind Earth's orbit and no impact is anticipated. Eruptions potentially associated with the C8.9 are currently being analyzed. Radio blackouts reaching the R1 levels were observed over the past 24 hours. The largest was on Apr 9th 2026 at 08:45 UTC.
ÿ
Solar activity is expected to be at low levels over April 9 to 11, with a chance for M-class (R1-R2/minor-moderate) flares and a slight chance for X-class (R3/strong or greater) flares, driven primarily by the flare potential of Regions 4409 and 4414. The greatest expected 3 hr Kp for Apr 09 through Apr 11 2026 is 5 (.33NOAA scale G1).

A brief description of Sunspots can be found on the Space Weather
Prediction Center website at, https://www.swpc.noaa.gov/phenomena/sunspotssolar-cycle[1]ÿ.
ÿ
Solar wind parameters reflected the transition out of a waning negative polarity coronal hole high speed stream (CH HSS) into nominal conditions. Wind speeds continued to decline from a peak of ~500 km/s to near 400 km/s by the end of the period.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, April 9, 2026, by F. K. Janda, OK1HH:

Perhaps the biggest surprise in recent days was that, following the geomagnetic disturbance of April 2-3 (which had been expected, albeit a day earlier and with lower intensity), there were no further major surprises. Solar activity declined as predicted, whereas because it declined over a relatively long period, there was a greater-than-expected drop in critical frequencies in the F2 ionospheric region at mid-latitudes.

For forecasting developments in the second third of April, the 27-day cycle could serve as a relatively reliable guide this time. First of all, one might expect a one- to two-day increase in geomagnetic activity (which is also indicated by the presence of solar coronal holes near the central meridian), followed by relative calm. This is despite the short time that has elapsed since the eleven-year peak of solar activity.

The Predicted Planetary A Index for April 4 to April 10 is 5, 4, 3, 2, 2, 2, and 2 with a mean of 2.8. The Predicted Planetary K Index is 18, 10, 8, 7, 5, 4, and 7 with a mean of 8.4. 10.7 centimeter flux is 106, 105, 108, 110, 115, 115, and 120 with a mean of 111.2.

For more information concerning shortwave radio propagation, see http://www.arrl.org/propagation[2]ÿand the ARRL Technical Information
Service web page at,ÿhttp://arrl.org/propagation-of-rf-signals[3]. For
an explanation of numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere[4]ÿ. Information and
tutorials on propagation can be found at,ÿhttp://k9la.us/[5]ÿ.

Also, check this:

https://bit.ly/3Rc8Njt[6]

"Understanding Solar Indices" from September 2002ÿQST.


[1] https://www.swpc.noaa.gov/phenomena/sunspotssolar-cycle
[2] http://www.arrl.org/propagation
[3] http://arrl.org/propagation-of-rf-signals
[4] http://arrl.org/the-sun-the-earth-the-ionosphere
[5] http://k9la.us/
[6] https://bit.ly/3Rc8Njt
---
þ Synchronet þ Whiskey Lover's Amateur Radio BBS