[SFDX] ARLP023 The ARRL Solar Report

Mon Jun 8 11:10:03 EDT 2026

ARLP023 The ARRL Solar Report

SB PROP @ ARL $ARLP023

ARLP023 Propagation Forecast

ZCZC AP23

QST de W1AW

Propagation Forecast Bulletin 23 ARLP023

 From ARRL Headquarters

Newington, CT June 5, 2026

To all radio amateurs

SB PROP ARL ARLP023

ARLP023 The ARRL Solar Report

Solar activity went from low to high this week. Activity was dominated 
by Region 4455, which produced frequent C-class flares alongside three 
significant flare events: an M9.3/Sf on June 1; as well as an M7.7/1b 
and an X1.0/1n on June 3.

There are eight numbered regions on the visible disk. Region 4455 
remains complex, maintaining its anti-Hale configuration and displaying 
a newly developed delta structure. Continuous flux emergence and spot 
growth with penumbral development were observed just ahead of its 
mature, positive polarity lead spot. Regions 4458 and 4459 both showed 
growth and consolidation, with Region 4459 showing rapid spot 
development in its trailing area and gaining a mixed-polarity gamma 
configuration. Region 4461 also showed flux emergence driving a gamma 
configuration, though extreme foreshortening near the limb limits 
high-confidence analysis of its overall complexity. Region 4462 
consolidated and showed increased separation between its poles. The 
remaining regions were stable or in decline.

Several eruptive events occurred during the reporting period. An M9.3/Sf 
flare June 1 was accompanied by wideband radio emissions, including a 
Type IV radio sweep with an estimated shock velocity of 253 km/s, and a 
10.7-cm radio burst. An associated coronal mass ejection (CME) became 
visible in LASCO C2 imagery on June 2. While faint in coronagraph 
imagery, GOES/SUVI imagery implies a partial to full halo profile, and 
COR2 triangulation confirms an Earth-directed component. Modeling 
indicates this event is the most Earth-directed CME of the period s events.

The M7.7/1B flare on June 3 was accompanied by wideband radio emissions, 
including a Type IV sweep, a Type II sweep with an estimated shock 
velocity of 313 km/s, and a prominent three-minute 10.7-cm radio burst. 
The associated CME was first seen in LASCO C2 on June 3. GOES/SUVI 304 
imagery shows much of the ejecta was deflected significantly northward 
by an adjacent positive polarity coronal hole. STEREO COR2 imagery and 
modeling shows that, while it retains an Earth-directed glancing 
component, it is the least directly-targeted event of the period.

Solar activity is expected to be at moderate to high levels through June 
6. M-class (R1-R2/minor-moderate) flaring remains likely, with a slight 
chance for X-class (R3/strong or greater) events, primarily due to the 
eruptive capabilities of Regions 4455, 4458, and 4459.

Solar wind parameters continued to be slightly elevated with conditions 
reflecting possible embedded transient influences. Wind speeds held 
steady near 400 km/s for most of the period before a distinct increase 
to near 450 km/s late in the period. The phi angle showed a distinct 
transition into the positive (away from the Sun) sector late in the period.

Mild enhancements are expected early on June 4 under the initial onset 
of positive polarity high-speed stream (+CH HSS) influences. Conditions 
will escalate dramatically mid-to-late on June 4 with the arrival of the 
multiple June 3 CMEs. These significant enhancements are expected to 
persist through June 5 with elevated conditions persisting through June 6.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's 
Ionosphere, June 4, 2026, by F. K. Janda, OK1HH:

On May 28, a large sunspot group, AR 4455, began to emerge on the 
northeastern limb of the solar disk. Its activity had already been 
monitored in the preceding days by the Solar Orbiter spacecraft, while 
we were also aware of it thanks to helioseismological observations. In 
the first days of June, AR 4455 gradually grew, while its configuration 
pointed to future growth in eruptive activity. A series of moderately 
energetic eruption eruptions on June

2 turned out to be precursors. The main event, featuring four 
energetically significant eruptions, took place on June 3, with at least 
two of them accompanied by a coronal mass ejection (CME), while at least 
one of which was headed directly toward Earth.

These lines you are currently reading are being written on June 4 at 
around 16:00 UT, just before more than one particle cloud is expected to 
hit Earth, marking the start of a geomagnetic disturbance. The 
disturbance is expected to intensify on June 5 and is likely to 
continue, albeit with lower intensity, on June 6.

The latest development in solar activity therefore differs significantly 
from what we witnessed in May, during the previous solar rotation, when 
solar activity was low and the magnetosphere remained calm in the 
following days.

Conclusion: Ionospheric propagation conditions during the first weekend 
of June will be variable and generally poor, with low MUF values. 
Although a noticeable improvement is expected in the coming days due to 
increased solar activity, another geomagnetic disturbance can be 
expected as early as June 10. The only certainty is change!

The latest solar report from Dr. Tamitha Skov, WX6SWW, can be found on 
Youtube at *https://www.youtube.com/watch?v=P0J2EQJWKIA 
<https://arrl.informz.net/z/cjUucD9taT0zNjQ4NTY1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzI2OTAyMw/index.html>*

The Predicted Planetary A Index for June 6 to June 12 is 8, 5, 5, 5, 5, 
30, and 25 with a mean of 11.9. The Predicted Planetary K Index is 3, 2, 
2, 2, 2, 6, and 5 with a mean of 3.1. 10.7 centimeter flux is 125, 125, 
120, 120, 130, 135, and 135 with a mean of 127.1.

For more information concerning shortwave radio propagation, see 
*www.arrl.org/propagation 
<https://arrl.informz.net/z/cjUucD9taT0zNjQ4NTY1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzI2OTAyNA/index.html>* 
and the ARRL Technical Information Service web page at 
www.arrl.org/propagation-of-rf-signals. For an explanation of numbers 
used in this bulletin, see

*www.arrl.org/the-sun-the-earth-the-ionosphere 
<https://arrl.informz.net/z/cjUucD9taT0zNjQ4NTY1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzI2OTAyNQ/index.html>*. 
Information and tutorials on propagation can be found at *http://k9la.us 
<https://arrl.informz.net/z/cjUucD9taT0zNjQ4NTY1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzI2OTAyNg/index.html>*.

NNNN

/EX

ARRL The National Association for Amateur Radio®

<https://arrl.informz.net/InformzDataService/mailing/bcd/bWFpbGluZ0luc3RhbmNlSWQ9MzY0ODU2NSZzdWJzY3JpYmVySWQ9NTI1NDczNjY0> 

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