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 [
http://www.arrl.org/propagation?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] and the ARRL Technical Information Service web page at www.arrl.org/propagation-of-rf-signals [
http://www.arrl.org/propagation-of-rf-signals?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] . For an explanation of numbers used in this bulletin, see www.arrl.org/the-sun-the-earth-the-ionosphere [
http://www.arrl.org/the-sun-the-earth-the-ionosphere?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] . Information and tutorials on propagation can be found at
http://k9la.us [
http://k9la.us ] .
Also, check this: "Understanding Solar Indices" from September 2002 QST.
https://bit.ly/3Rc8Njt [
https://bit.ly/3Rc8Njt ]
NNNN
/EX
ARRL The National Association for Amateur Radio(R)
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