SB PROP @ ARL $ARLP030
ARLP030 The ARRL Solar Report

ZCZC AP30
QST de W1AW
Propagation Forecast Bulletin 30 ARLP030

From ARRL Headquarters

Newington CT August 15, 2025
To all radio amateurs

SB PROP ARL ARLP030
ARLP030 The ARRL Solar Report

Solar activity has been at low levels with mostly weak C-class flares
observed from Regions 4172 and 4180. The largest flare of the period was a C6.8/Sf at 15/1037 UTC from Region 4172. There are 12 regions on the disk
with most being simple in magnetic complexity. Region 4172 remained the
largest region on the disk and continued to decay with its magnetic field decreasing in complexity. All remaining regions were quiet and stable.


No Earth-directed CMEs were observed in available coronagraph imagery.

Solar activity is likely to continue at low levels through 17 August. Despite their decreasing activity, Region 4172 will help maintain a slight chance
(35%) for isolated M-class flares (R1-2/Minor-Moderate radio blackouts) in
the forecast through 15 August. Chances decrease to 30% as the region moves beyond the western limb.


Waning influences from the CH HSS will steadily decrease the flux of 2 MeV electrons, but concentrations at geostationary orbit will remain high most likely through 17 August. Last rotation, electrons remained significantly
above the 1,000 pfu threshold for seven days with diurnal maximas above threshold for 11 days.


Solar activity is expected to be at predominately low levels with M-class
flare (R1-R2/Minor-Moderate events) activity likely over 11 August to 06 September.


No proton events are expected at geosynchronous orbit, barring significant flare activity.


Geomagnetic field activity is expected to reach active levels on 11 August
due to waning positive polarity CH HSS influence.

Periods of minor storming are likely on 18-20 August, with periods of active conditions likely on 22 August, due to negative polarity CH HSS influence.

Active conditions are likely again on 28 August in response to anticipated negative polarity CH HSS influence.

Periods of moderate storming are likely on 05 September, with active levels likely on 04 and 06 September, due to positive polarity CH HSS influence.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere
for August 14, 2025 by F. K. Janda, OK1HH:


The overall level of solar activity did not change significantly in August. Medium-size flares were observed almost daily in one or two sunspot groups, while the parameters of the solar wind were most influenced by a coronal hole in the southwestern part of the solar disk.

This clear situation made it possible to correctly predict the positive phase of the geomagnetic disturbance on August 8 (G1), which manifested itself in improved conditions for ionospheric propagation of short waves.

Particles from the solar flare on August 5 and the intensification of the
solar wind from the coronal hole contributed to the disturbance.

This was followed by a negative phase of the disturbance (G2), during which propagation conditions deteriorated significantly.

This was followed by only slightly turbulent development.

The development after August 15 should be calmer, as there are currently no major active areas near the emerging coronal hole in the northeast of the
solar disk.


The Predicted Planetary A Index for August 16 to 22 is 5, 5, 15, 25, 15, 8,
and 12, with a mean of 12.1. Predicted Planetary K Index is 2, 2, 5, 5, 5, 3, and 4, with a mean of 3.7. 10.7 centimeter flux is 145, 150, 145, 145, 145, 140, and 145, with a mean of 145.


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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SB PROP @ ARL $ARLP030
ARLP030 Propagation Forecast

ZCZC AP30
QST de W1AW
Propagation Forecast Bulletin 30 ARLP030

From ARRL Headquarters

Newington, CT July 24, 2026
To all radio amateurs

SB PROP ARL ARLP030
ARLP030 The ARRL Solar Report

Solar activity continued at moderate levels as Region 4493 produced an M3.6 flare on July 22, which was the largest event of the period and was
associated with a 10.7-centimeter radio burst of 200 solar flux units (sfu). Additionally, 4493 produced a C3.4 flare on July 22, which was associated
with another 10.7-cm radio burst of 150 sfu.


Region 4493 continued to undergo consolidation in its leading and trailing spots, but showed signs of new flux emergence in its intermediate area during the early hours of the reporting period. Region 4494 developed new, simple spots, but remained uni-polar. The remaining two numbered active regions were relatively stable and quiet.


A filament eruption NW of Region 4493 on July 21 was modeled and assessed to
be at least partially Earth-directed. While modeling efforts suggest that a bulk of the material should pass north and ahead of Earth's orbit, this is
low confidence given the faintness of this event in Sun-Earth line-focused coronagraph imagery and compounded by likely interaction with the coronal
hole in the vicinity of the source location.


Additional M-class flare activity (R1-R2 radio blackouts) is likely through July 25 primarily due to the flare potential currently exhibited by AR 4493.


Solar wind parameters were mildly enhanced under a sustained negative
polarity coronal hole high-speed stream (CH HSS) regime and a possible secondary Co-rotating Interaction Region (CIR). Solar wind speeds were
roughly between 400 and 482 km/s.


The current regime is expected to largely continue through July 25.
Additional enhancements are possible beginning late on July 23 due to a
coronal mass ejection (CME) that left the sun on July 20, with stronger enhancements arriving by early on July 24 with the arrival of the aforementioned CME event from July 21.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, July 23, 2026, by F. K. Janda, OK1HH:


A relatively large sunspot group, which was already very conspicuous in
images from the SOLAR ORBITER spacecraft, was designated NOAA 4493 after its discovery as an active region on the northeastern limb of the solar disk.

It produced class C and M flares on a daily basis.
It is currently located in the northwest of the solar disk.
As it grew, it disrupted a long north-south coronal hole and remains the largest and most complex sunspot group on the visible disk, accounting for
most of the observed eruptive activity.

The eruption observed within it on July 20 was accompanied by a CME.
The ejected particles triggered a geomagnetic disturbance on the afternoon of July 23.


As a result of this activity, the ionosphere is currently undergoing variable conditions, characterized albeit irregularly by a pronounced presence of the summer sporadic E layer in the Earth s northern hemisphere.

In the coming days, geomagnetic activity should begin to gradually decline
(no earlier than July 25). Increased solar activity will likely persist
almost until the end of the month.

Conditions for ionospheric radio propagation will therefore remain variable, with irregular occurrences of relatively very favorable days.


The predicted Planetary A Index for July 25 to 31 is 5, 5, 5, 5, 5, 5, and 5, with a mean of 5.0. The predicted Planetary K Index is 2, 2, 2, 2, 2, 2, and
2, with a mean of 2.0. The predicted 10.7 centimeter flux is 125, 125, 120, 118, 118, 115, and 112, with a mean of 119.0.


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)