SB PROP @ ARL $ARLP028
ARLP028 The ARRL Solar Report

ZCZC AP28
QST de W1AW
Propagation Forecast Bulletin 28 ARLP028

From ARRL Headquarters

Newington CT August 1, 2025
To all radio amateurs

SB PROP ARL ARLP028
ARLP028 The ARRL Solar Report

Spaceweather.com reports solar activity was at low levels with only minor C-class flares observed.

Region 4154 produced a C1.4 flare on 31 July. Region 4153 contributed the majority of the flares, including a C1.3 flare, a C1.5/Sf flare, and a C1.6 flare on 31 July. Both of these regions remained mostly unchanged during the period.

Region 4166 exhibited growth during the period, yet remained mostly inactive. Newly numbered Region 4167 exhibited growth during the period and produced a C1.9/Sf flare. The remaining regions were stable or in decay.


Solar activity is expected to be low with a chance for M-class flares, Minor-Moderate, through 03 August.


Solar wind parameters are expected to continue a waning trend on 01 August as the negative polarity CH HSS moves from its geoeffective location. An additional disturbance cannot be ruled out for 02 August due to the 30 July
CME event mentioned in the previous discussion. Aside from the possible CME influence, conditions are expected to remain at mostly background levels through 03 August.


Quiet conditions, with isolated unsettled periods, are expected to prevail on 01 August as CH HSS effects gradually wane. Quiet to unsettled levels are expected on 02 to 03 August, with a slight chance for an isolated active
period on 02 August, due to the possible July CME passage.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere
for July 31, 2025 by F. K. Janda, OK1HH:


We are most likely still in the period of the maximum of 11-year solar
activity cycle No.

25. Its peak was preliminarily recorded in the fall of 2024, but this year's course was very unusual, while its response in the ionosphere was unexpected, especially in May and June.

Solar activity should continue to decline slowly this year, with a more rapid decline expected starting in 2026. Therefore, there is still hope for
favorable shortwave propagation conditions this fall, especially in the
shorter part of the range (say, at frequencies above 20 MHz).


Last week, only relatively small sunspot groups were observed on the Sun,
with no major flares.

This was accompanied by smaller fluctuations in the speed of the solar wind and, therefore, a calmer geomagnetic field.

Although the summer season in the northern hemisphere of the Earth is not favorable for long-distance shortwave propagation, it was still an
improvement over previous months.

There should be fewer sunspot groups on the far side of the Sun.
But it seems that those that will soon appear will be larger than those we
are currently observing.


Solar ultraviolet and X-ray radiation, together with the solar wind, are the main causes of changes in the Earth's ionosphere, but they are not the only ones.

The ionosphere also reacts to processes taking place below it.
These include gravitational waves (formed at the interface between air masses of different densities, for example in meteorological fronts) and infrasound caused by earthquakes and typhoons.

Scientific research into these phenomena is still in its infancy, and
although records of changes in the ionosphere following the earthquake on the east coast of Kamchatka (M8.8, Tue 29 July 2025, 23:24:51 UTC) are available, for DX signal hunters this is still more of a curiosity.


The latest solar report from Dr. Tamitha Skov, WX6SWW, can be found on
YouTube at www.youtube.com/watch?v=-XM4kZ-vvRk [ ttps://www.youtube.com/watch?v=-XM4kZ-vvRk ]


The Predicted Planetary A Index for August 2 to 8 is 5, 5, 12, 8, 5, 20, and 15, with a mean of 10. Predicted Planetary K Index is 2, 2, 4, 3, 2, 5, and
4, with a mean of 3.1. 10.7 centimeter flux is 140, 150, 155, 155, 155, 155, and 160, with a mean of 152.9.


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 [ http://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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SSB PROP @ ARL $ARLP028
ARLP028 Propagation Forecast

ZCZC AP28
QST de W1AW
Propagation Forecast Bulletin 28 ARLP028

From ARRL Headquarters

Newington, CT July 10, 2026
To all radio amateurs

SB PROP ARL ARLP028
ARLP028 The ARRL Solar Report

Solar activity reached moderate levels with an M1.5/1N flare on July 8 from Region 4482. There are currently five numbered regions on the visible disk. Region 4482 demonstrated continued growth and developed a delta spot within
its trailing spot group. Region 4485 displayed new flux emergence. Regions
4486 and 4487 were newly numbered during the period. Region 4481 was stable
and remained an unremarkable unipolar group. No Earth-directed CMEs were observed in available coronagraph imagery.


Solar activity is expected to remain at low levels through July 11, with a
high chance for M-class (R1-R2/minor-moderate) flares and a slight chance for X-class (R3/strong and greater) events. This flare probability is almost entirely due to the complexity and potential of Region 4482.


Solar wind parameters reflected near ambient background conditions. Solar
wind speeds were generally near 400 km/s. The phi angle was predominantly in the positive sector.


Enhancements are anticipated to begin on July 9 and continue through July 11 with the arrival of a co-rotating interaction region (CIR) ahead of a
negative polarity coronal hole high-speed stream (-CH

HSS).

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, July 9, 2026, by F. K. Janda, OK1HH:


The power flux of solar radio noise at a frequency of 2800 MHz (at a
wavelength of 10.7 cm), which is measured precisely every day at noon local time in Penticton, Canada, and is referred to as the solar flux, remains at
a relatively low level.

The reason is that the number of observed sunspot groups on the solar disk dropped to just three on July 7, the lowest number recorded during a single solar rotation (the following day, their number increased to five). The
largest active region, NOAA 4482, which we observe in the southeast of the solar disk, has not changed significantly in size and continues to produce moderate-intensity flares on a regular basis.

All three coronal holes are currently relatively far from it.
The intensity of the solar wind is changing only slightly; periods of
increased geomagnetic activity alternate with quiet days, making it
impossible to accurately predict future developments.


A more pronounced increase in solar activity is expected in the second half
of July (with a gradual increase in solar flux up to 180 s.f.u.). More significant geomagnetic activity can be expected if major solar flares occur, especially if they occur near or west of

the central meridian. This is likely to happen sometime in the second half of July.


The predicted Planetary A Index for July 11 to 17 is 12, 8, 5, 5, 5, 10, and
8, with a mean of 7.6. The predicted Planetary K Index is 4, 3, 2, 2, 2, 3,
and 3, with a mean of 2.7. 10.7 centimeter flux is 125, 120, 125, 130, 135, 135, and 135, with a mean of 129.3.


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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