SB PROP @ ARL $ARLP029
ARLP029 The ARRL Solar Report

ZCZC AP29
QST de W1AW
Propagation Forecast Bulletin 29 ARLP029

From ARRL Headquarters

Newington CT August 8, 2025
To all radio amateurs

SB PROP ARL ARLP029
ARLP029 The ARRL Solar Report

Solar activity was at low levels on 28 July to 02 August and moderate levels
on 03 August. The largest flare of the period was an M2.9/2b event observed from Region 4168 on 03 August. The region also produced numerous C-class events. Numerous C-class activity was observed from Regions 4153, 4155, and 4167. No Earth-directed CME activity was observed.


No proton events were observed at geosynchronous orbit.

Geomagnetic field activity was at quiet to unsettled levels the entire highlight period. A single active period was observed late on 03 August. A majority of the unsettled periods was due to weak negative polarity CH HSS influence. Solar wind speeds were at mostly 400 km/s from 28 July through midday on 30 July and 475-500 km/s from midday 30 July through 03 August with
a peak velocity observed at 600 km/s late on 03 August.


Solar activity is expected to be at mostly low levels with a chance for
M-class flares for the outlook period.


Geomagnetic field activity is expected to be at active to G1 storm levels on
11 to 15 August, 18 to 22 August, and 25 to 30 August due to recurrent CH HSS effects. Quiet to unsettled levels are expected on the remaining days of the outlook period.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere
for August 7, 2025 by F. K. Janda:


Overall solar activity has not changed much in recent days, but it has been higher than on the same days of the previous solar cycle.

However, eruption activity increased in the northwestern part of the solar disk.

The M4.4 eruption on May 5, with a maximum at 1553 UTC, was of greatest significance for further development, as it was accompanied by a CME, part of which is heading toward Earth.

It is expected to arrive on August 8, at the same time as a co-rotating interactive region (CIR), should cause an intensification of the solar wind blowing from a large coronal hole in the southern hemisphere of the Sun.


The combination of these two phenomena will cause an increase in geomagnetic activity on August 8. Thanks to the intensified solar wind, the geomagnetic field will remain active on May 9. On the first day, there will likely be a positive phase of development, accompanied by an increase in the highest
usable frequencies of the F2 ionospheric region, while on the second day, the development will transition to a negative phase, with a decrease in usable frequencies and an overall deterioration in shortwave propagation conditions due to increased attenuation.


After that, rather turbulent developments can be expected until approximately August 12, followed by a calming down from August 13. Overall solar activity should remain only slightly elevated.


The latest report from Dr. Tamitha Skov can be found on YouTube at https://www.youtube.com/watch?v=SItdIe1X7RU [ https://www.youtube.com/watch?v=SItdIe1X7RU ]


The Predicted Planetary A Index for August 9 to 15 is 5, 5, 25, 18, 20, 12,
and 8, with a mean of 13.2. Predicted Planetary K Index is 2, 2, 5, 5, 5, 4, and 3, with a mean of 3.7. 10.7 centimeter flux is 135, 135, 130, 130, 130, 135, and 135, with a mean of 132.9.


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://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. Information and tutorials on propagation can be found at http://k9la.us [ http://k9la.us/ ] .


Also check "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)
Unsubscribe [ http://www.arrl.org/opt-in-out?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
]



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SB PROP @ ARL $ARLP029
ARLP029 Propagation Forecast

ZCZC AP29
QST de W1AW
Propagation Forecast Bulletin 29 ARLP029

From ARRL Headquarters

Newington, CT July 17, 2026
To all radio amateurs

SB PROP ARL ARLP029
ARLP029 The ARRL Solar Report

Solar activity has remained at low levels, with an occasional low-level
C-class flaring observed, including a C3.3/Sf flare on July 15 from Region 4489. The largest event of the period, a long-duration C8.9 flare that peaked on July 15, originated from a returning region on the eastern limb.

This region is not yet numbered and will be assessed once it has become
visible from Earth¡s perspective, but the latest imagery from Solar Orbiter suggested only a simple and rather average bipolar group with a relatively small penumbra.


There are two numbered sunspot regions on the visible disk.
Region 4482 showed minor new flux emergence behind its mature primary spot, developing a bipolar configuration.

As Region 4489 rotated further into view and limb foreshortening effects decreased, very small opposite-polarity trailing spots became visible, making it a stable bipolar group.

Additionally, a small, magnetically simple, region tracked in Solar Orbiter imagery has begun to rotate over the east limb near S10. No Earth-directed
CMEs were observed in available coronagraph imagery.


Solar activity is expected to remain at low levels through July 18, with a slight chance for M-class (R1-R2/minor-moderate) flares, primarily driven by active regions anticipated to rotate onto the visible disk over the next few days.


Solar wind parameters reflected possible combined glancing coronal mass ejection (CME) effects and subsequent weak positive polarity coronal hole high-speed stream (+CH HSS) influences.


A return to more ambient-like conditions is expected over the next three
days.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, July 16, 2026, by F. K. Janda, OK1HH:


The significant decline in solar activity throughout the first half of July
is clearly illustrated by the solar flux values, which fell from 203 s.f.u. (July 2) to 100 s.f.u. (July 14¤15), as well as by the number of sunspot groups, which dropped from five to two.

A significant drop in the critical frequencies of the F2 layer began as early as July 4 during the geomagnetic disturbance of July 4¤5, and due to the
sharp decline in solar activity, these values returned to average levels only very slowly in the following days.

Consequently, the sporadic E layer had an even greater impact on shortwave propagation (particularly in the mid-latitudes of Europe on July 14 and 16).


The increase in solar activity, which is expected to begin as early as the
end of this week and should last nearly until the end of the month, will
result in significantly better shortwave propagation conditions than those experienced in the first half of the month. More significant changes
(possibly an initial rise, but then very likely a temporary drop in MUF) will likely be caused by a geomagnetic disturbance, which is tentatively expected
on July 21 and 22.


The predicted Planetary A Index for July 18 to 24 is 5, 5, 5, 5, 12, 10, and
7, with a mean of 7.0. The predicted Planetary K Index is 2, 2, 2, 2, 4, 3,
and 2, with a mean of 2.4. Predicted 10.7 centimeter flux is 135, 135, 135, 135, 135, 135, and 135, with a mean of 135.0.


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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* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)