[SFDX] ARLP025 The ARRL Solar Report

[Bill]

ARLP025 The ARRL Solar Report

	

SB PROP @ ARL $ARLP026

ARLP026 Propagation Forecast

ZCZC AP26

QST de W1AW

Propagation Forecast Bulletin 26 ARLP026

 From ARRL Headquarters

Newington, CT June 26, 2026

To all radio amateurs

SB PROP ARL ARLP026

ARLP026 The ARRL Solar Report

Solar activity has remained at low levels, with frequent C-level 
activity in the SE quadrant of the solar disk. The largest flare of the 
period was a C3.8 on June 24 from Region 4478, which is the large 
sunspot that Solar Orbiter had been tracking across the Sun ís far side.

While the majority of the flaring activity this period came from 4478, 
Region 4475 also produced several small C-flares as additional trailing 
spots began to emerge.

Regions 4472 and 4473 continued to decay throughout the period.

Region 4479 was numbered this period. No Earth-directed CMEs were 
observed in available coronagraph imagery.

Solar activity is expected to continue at predominately low levels on 
June 25 to 27 with a high chance for M-flares (R1-R2/minor-moderate) and 
a slight chance for X-flares (R3/strong), primarily due to the potential 
of Region 4478.

Solar wind parameters were elevated this period from a mix of negative 
polarity coronal hole high speed stream (CH HSS) onset and minor 
magnetic transient influences.

The solar wind speed began the period averaging 350 km/s, then increased 
sharply on June 24 to ~450 km/s. This was followed by another notable 
jump in speed, also beginning June 24, ending the reporting period at 
approximately 600 km/s. Phi was predominantly negative (towards the 
Sun). Solar wind conditions are expected remain elevated/disturbed 
through June 27 due to the continued influence of the negative polarity 
coronal hole high speed stream.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's 
Ionosphere June 26 by F.K. Janda, OK1HH: After the last and largest 
sunspot group in the chain as observed by the Solar Orbiter appeared on 
the southeastern limb of the solar disk, we can expect another increase 
in solar activity to a level somewhat higher than expected. At the same 
time, there are three coronal holes near the central meridian, with 
additional active regions just ahead of them.

As a result, the solar wind intensified significantly on June 24, 
triggering a geomagnetic disturbance. The maximum southern (i.e., 
longitudinal) component of Bz reached -12 nT, whereas this trend appears 
set to continue through June 27. This will result in highly variable 
shortwave propagation conditions. Furthermore, propagation will be more 
affected by the sporadic E layer than in recent days.

The Predicted Planetary A Index for June 27 to July 3 is 8, 5, 5, 5, 5, 
5, and 18 with a mean of 7.3. The Predicted Planetary K Index is 3, 2, 
2, 2, 2, 2, and 5 with a mean of 2.6. 10.7 centimeter flux is 130, 130, 
132, 135, 145, 138, and 140 with a mean of 135.7.

For more information concerning shortwave radio propagation, see 
www.arrl.org/propagation 
<https://arrl.informz.net/z/cjUucD9taT0zNjY1NzEzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzU2MDA4NQ/index.html> 
and the ARRL Technical Information Service web page at 
www.arrl.org/propagation-of-rf-signals 
<https://arrl.informz.net/z/cjUucD9taT0zNjY1NzEzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzU2MDA4Ng/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/cjUucD9taT0zNjY1NzEzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzU2MDA4Nw/index.html>. 
Information and tutorials on propagation can be found at http://k9la.us 
<https://arrl.informz.net/z/cjUucD9taT0zNjY1NzEzJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzU2MDA4OA/index.html>.

NNNN

/EX

	

	

ARRL The National Association for Amateur Radio®


	

<https://arrl.informz.net/InformzDataService/mailing/bcd/bWFpbGluZ0luc3RhbmNlSWQ9MzY2NTcxMyZzdWJzY3JpYmVySWQ9NTI1NDczNjY0> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/sfdxa/attachments/20260627/9d4a0ac2/attachment-0001.html>