[SFDXA] ARLP041 The ARRL Solar Report

[Bill]

ARLP041 The ARRL Solar Report

	

SB PROP @ ARL $ARLP041

ARLP041 The ARRL Solar Report

ZCZC AP41

QST de W1AW

Propagation Forecast Bulletin 41 ARLP041

 From ARRL Headquarters

Newington CT, October 31, 2025

To all radio amateurs

SB PROP ARL ARLP041

ARLP041 The ARRL Solar Report

Solar activity has decreased to very low levels. Region 4266 exhibited 
signs of slight development as it gained asymmetric penumbra surrounding 
its trailing spots. Meanwhile, Region 4267 underwent decay, losing 
several leading spots. Additional activity included a coronal mass 
ejection (CME) off the NE limb on October 29.

An associated Type II radio sweep was reported with the CME; however, 
SUVI 195 imagery revealed the CME to have originated on the far side. 
Also, an approximate 12-degree filament eruption, centered near N27W24, 
was observed becoming unstable beginning on October 29. Most of the 
material of this event appeared to have been reabsorbed, with perhaps a 
faint and narrow CME escaping. Modeling of this event revealed a 
possible glancing blow to the north of Earth by late on November 2, but 
confidence is low in both the analysis of this event and the modeling 
outcome.

Solar wind parameters continued to reflect positive polarity coronal 
hole high-speed stream (CH HSS) influences. Solar wind parameters are 
expected to continue to reflect positive CH HSS influences through 
November 1.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's 
Ionosphere, October 30, 2025, by F. K. Janda, OK1HH:

"It is very rare for the situation on the Sun and between it and Earth 
to be as relatively simple and clear as it has been in recent days. This 
is one of the reasons why it was possible to make a fairly accurate 
prediction of further developments. Although there were concerns that an 
intensified solar wind could hit Earth as early as October 26, the 
original forecast ultimately proved accurate, and the disturbance began 
on October 28. The last weekend in October was thus marked by relatively 
good conditions for radio wave propagation on all shortwave bands.

"Regular helioseismological observations of the far side of the Sun are 
closely monitoring the only two currently active regions on the Sun. 
They will begin to emerge on the eastern edge of the solar disk in the 
first half of next week, which will immediately be reflected in an 
increase in solar flux. This may peak around October 10, but it seems 
that it will happen sooner.

"The increase in solar activity during the usual favorable seasonal 
changes alone will result in improved conditions for shortwave 
propagation. With a little luck, the improvement could peak around 
November 8, when the next increase in geomagnetic activity can be expected."

Solar activity is expected to be at moderate levels until November 15 
due to the return of Region 4246. Low levels are expected to prevail 
from November 14 to 22 as multiple regions depart the visible disk.

A greater than 2 MeV electron flux at geosynchronous orbit is expected 
to be at high levels until November 15 due to responses from recurrent 
CH HSS influences. Moderate levels are expected from November 16 to 22.

Geomagnetic field activity is expected to be at quiet to unsettled 
levels on November 1 to 6, 10 to 14, and November 16 to 22. Active 
conditions are expected from November 7 to 9 and November 15.

The latest video report from Dr. Tamitha Skov, WX6SWW, can be found on 
YouTube at https://www.youtube.com/watch?v=y8uEPcivbQ8 
<https://arrl.informz.net/z/cjUucD9taT0zNDc3Mjk5JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDM2MDI5OQ/index.html>.

Spaceweather.com for October 31 reports on "Halloween Fireballs" and the 
rapid brightening of Comet 3I/ATLAS.

The Predicted Planetary A Index for November 1 to 7 is 8, 5, 5, 5, 5, 5, 
8, and 12, with a mean of 6.9. Predicted Planetary K Index is 3, 2, 2, 
2, 2, 3, and 4, with a mean of 2.6. 10.7-centimeter flux is 130, 130, 
135, 140, 140, 140, and 140, with a mean of 136.4.

For more information concerning shortwave radio propagation, see 
www.arrl.org/propagation 
<https://arrl.informz.net/z/cjUucD9taT0zNDc3Mjk5JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDM2MDMwMA/index.html> 
and the ARRL Technical Information Service web page at 
www.arrl.org/propagation-of-rf-signals 
<https://arrl.informz.net/z/cjUucD9taT0zNDc3Mjk5JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDM2MDMwMQ/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/cjUucD9taT0zNDc3Mjk5JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDM2MDMwMg/index.html>. 
Information and tutorials on propagation can be found at http://k9la.us 
<https://arrl.informz.net/z/cjUucD9taT0zNDc3Mjk5JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDM2MDMwMw/index.html>.

NNNN

/EX

	

	

ARRL The National Association for Amateur Radio®

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