[SFDXA] ARLP014 The ARRL Solar Report

[Bill]

ARLP014 The ARRL Solar Report

	

SB PROP @ ARL $ARLP014

ARLP014 Propagation Forecast

ZCZC AP14

QST de W1AW

Propagation Forecast Bulletin 14 ARLP014

 From ARRL Headquarters

Newington, CT April 3, 2026

To all radio amateurs

SB PROP ARL ARLP014

ARLP014 The ARRL Solar Report

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.

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.

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.

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, 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 
www.arrl.org/propagation 
<https://arrl.informz.net/z/cjUucD9taT0zNTkzNTkzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MjMyMzI3MQ/index.html> 
and the ARRL Technical Information Service web page at 
www.arrl.org/propagation-of-rf-signals 
<https://arrl.informz.net/z/cjUucD9taT0zNTkzNTkzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MjMyMzI3Mg/index.html>. 
For an explanation of numbers used in this bulletin, see 
www.arrl.org/the-sun-the-earth-the-ionosphere 
<https://arrl.informz.net/z/cjUucD9taT0zNTkzNTkzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MjMyMzI3Mw/index.html>. 
Information and tutorials on propagation can be found at http://k9la.us 
<https://arrl.informz.net/z/cjUucD9taT0zNTkzNTkzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MjMyMzI3NA/index.html>.

NNNN

/EX

	

	

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