ARLP022 The ARRL Solar Report undefined

 

SB PROP @ ARL $ARLP022

ARLP022 Propagation Forecast

 

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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 at https://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, see and the ARRL Technical Information Service web page at . For an

explanation of numbers used in this bulletin, see

. Information and tutorials on propagation can be found at .

 

Also, check this: "Understanding Solar Indices" from September 2002

QST.

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/EX

 

 

ARRL The National Association for Amateur Radio®