[SFDXA] ARLP022 Propagation Forecast

[Bill]

SB PROP @ ARL $ARLP022

ARLP022 Propagation Forecast

ZCZC AP22

QST de W1AW

Propagation Forecast Bulletin 22 ARLP022

From ARRL Headquarters

Newington, CT May 29, 2026

To all radio amateurs

SB PROP ARL ARLP022

ARLP022 The ARRL Solar Report

Solar activity has remained at low levels this past week. The largest 
event of the period was a C3.4 flare originating from Region 4446. There 
are nine numbered regions on the visible disk. Region 4452 showed 
notable growth and new flux emergence. Region 4450 decayed to plage, 
though unassociated transitory pores were observed to its east and west. 
Region 4443 decayed into a unipolar spot as it approached the west limb 
following the loss of its leading components Regions 4453, 4454 and 4455 
were numbered during the period. Far-side satellite imagery from Solar 
Orbiter indicates that Region 4455 is likely a large bipolar group with 
its trailing opposite-polarity spots still located behind the east limb 
and was numbered proactively due to its flaring potential. All other 
regions either continued in slow decay or remained stable.

A faint, potentially partial-halo, coronal mass ejection (CME) first 
seen in LASCO C2 imagery on May 26 and subsequently in GOES/CCOR1 was 
analyzed. No obvious on-disk source exists. Modeling suggests a possible 
glancing blow at Earth on May 31. Additionally, narrow eruptions 
associated with flaring from newly numbered Region 4444 were seen in 
SUVI imagery but these features are well northward of the ecliptic plane 
with no Earth-directed components. No other Earth-directed coronal mass 
ejections (CMEs) were observed in available coronagraph imagery.

Solar activity is expected to be at low to moderate levels through May 
30. There remains a chance for isolated M-class flares 
(R1-R2/minor-moderate) driven by the eruptive potential of the southeast 
sunspot groups and newly numbered Region 4454.

Solar wind parameters remained slightly elevated and possibly indicative 
of weak negative polarity coronal hole high-speed stream (-CH 
HSS)influences.

Solar wind speeds varied modestly between 350 and 425 km/s. The phi 
angle was predominantly in the negative sector (towards the Sun), though 
minor deviations were observed later in the period. A return

toward near-background, nominal conditions is anticipated by May 30.

Weekly Commentary on the Sun, the agnetosphere, and the Earth's 
Ionosphere, May 28, 2026

Observations of the far side of the Sun by the Solar Orbiter probe 
showed us how a new and relatively large active region was approaching 
the northeastern limb of the solar disk. But it wasnít until it began to 
emerge on May 28 (designated as AR 4455) that it became clear the recent 
rise in solar activity would continue.

Furthermore, the only significant coronal hole in the higher northern 
heliographic latitudes is sufficiently far from other active regions, so 
we need not expect a significant intensification of the solar wind.

Therefore, we could expect calmer conditions in the Earthís 
magnetosphere and, at the same time, higher usable frequencies in the 
ionosphere for long-distance communications before their seasonal 
decline. However, summer in the ionosphere of the Earthís northern 
hemisphere, with higher attenuation in the lower ionosphere during the 
long days, will often be enlivened by sporadic E layers in the 
mid-latitudes until August.

The latest solar report from Dr. Tamitha Skov, WX6SWW, can be found on 
Youtube athttps://www.youtube.com/watch?v=CP3KYpDOZDA

The Predicted Planetary A Index for May 30 to June 5 is 5, 5, 5, 5, 5, 
15, and 5 with a mean of 6.4. The Predicted Planetary K Index is 2, 2, 
2, 2, 2, 4, and 2 with a mean of 2.3. 10.7 centimeter flux is 145, 145, 
145, 145, 150, 145, and 140 with a mean of 145.

For more information concerning shortwave radio propagation, 
seewww.arrl.org/propagation 
<https://arrl.informz.net/z/cjUucD9taT0zNjQyNzM5JnA9MSZ1PTU1NTg0MDIyMiZsaT00MzE4MTYzNg/index.html>and 
the ARRL Technical Information Service web page 
atwww.arrl.org/propagation-of-rf-signals 
<https://arrl.informz.net/z/cjUucD9taT0zNjQyNzM5JnA9MSZ1PTU1NTg0MDIyMiZsaT00MzE4MTYzNw/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/cjUucD9taT0zNjQyNzM5JnA9MSZ1PTU1NTg0MDIyMiZsaT00MzE4MTYzOA/index.html>. 
Information and tutorials on propagation can be found athttp://k9la.us 
<https://arrl.informz.net/z/cjUucD9taT0zNjQyNzM5JnA9MSZ1PTU1NTg0MDIyMiZsaT00MzE4MTYzOQ/index.html>.



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