[SFDXA] ARLP042 The ARRL Solar Report

[Bill]

ARLP042 The ARRL Solar Report

	

SB PROP @ ARL $ARLP042

ARLP042 The ARRL Solar Report

ZCZC AP42

QST de W1AW

Propagation Forecast Bulletin 42 ARLP042

 From ARRL Headquarters

Newington CT, November 7, 2025

To all radio amateurs

SB PROP ARL ARLP042

ARLP042 The ARRL Solar Report

Solar activity has reached high levels due to a pair of X-class flares.

The first was an X1.8 on November 4 from Region 4274. Associated with 
the flare were Type IV radio sweeps, 160 sfu Tenflare, and a partial 
halo coronal mass ejection (CME) directed mostly off the NE limb in 
coronagraph imagery. Although the majority of the ejecta is expected to 
pass behind Earth, there is the possibility of a shock enhancement late 
on November 6 to early on November 7. Region 4274 continued to be in a 
growth phase; however, the intermediate spots appeared to begin to 
separate from the larger trailing spots.

An X1.1 flare was also observed on November 4 from a region just beyond 
E limb near S15. Associated with this flare were a Type IV radio sweep 
and a non-Earth directed CME observed off the SE limb on November 4.

Solar wind parameters were mildly enhanced, but in decline. Solar wind 
speed decreased from approximately 480 km/s to nearly 420 km/s.

Solar activity is expected to be at moderate levels on November 3 to 17 
to the delayed return of Regions 4246 and 4248, that seem to be rotating 
into the Earthside solar disk between November 3 to 4. At least two 
other regions are expected to emerge from the East limb until November 
10, as observed at GONG farside images.

G1 storm is likely on November 7 to 8 due to reccurrence of CH HSS 
influences. R1/R2 radio blackouts are possible during the November 3 to 
9 period due to the returning Regions 4246 and 4248.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's 
Ionosphere, November 6, 2025, by F. K. Janda, OK1HH:

The minimum activity of the Sun during its last rotation was recorded at 
the end of October. The solar radio flux fell from 162 s.f.u., measured 
on October 15, to 115 s.f.u. on November 1. During the same period, the 
number of sunspot groups on the solar disk decreased from ten to two. 
However, coronal mass ejections, observed mainly near the eastern limb 
of the solar disk, indicated that the level of activity would soon 
increase rapidly.

The solar flux then began to rise quickly, reaching 159 s.f.u. on 
November 4. Energetically significant flares were produced mainly by 
active region No. 4274, while the Earth's atmosphere was hit by protons 
with energies up to 10 MeV. The significantly intensified solar wind was 
caused by the extensive coronal hole No. 94, which passes through the 
central meridian at the same time. The onset of the expected intense 
geomagnetic disturbance was predicted for November 6, but it began a day 
earlier. On the evening of November 5, it reached grade G3, with 
three-day indices up to K=6, while continued until the forenoon hours of 
UTC the following day. The effect on the ionosphere was very strong; 
from the beginning of the disturbance, MUF values dropped significantly 
and remained very low even on November 6.

It appears that active region No. 4274 has enough energy in reserve to 
continue its eruptive activity in the coming days. As the coronal hole 
No. 94 shows no signs of shrinking, we can expect not only a further 
increase in solar activity in the first half of November, but also 
several geomagnetic disturbances. The effects on the Earth's ionosphere 
will be highly probable. Although MUF values will often increase at the 
onset of disturbances, this will be followed by a decrease accompanied 
by increased attenuation. This will very often be accompanied by the 
scattering of radio waves on ionospheric inhomogeneities.

The latest video report from Dr. Tamitha Skov, WX6SWW, can be found on 
YouTube https://www.youtube.com/watch?v=Fx1goRRoBDg 
<https://arrl.informz.net/z/cjUucD9taT0zNDgzNDg1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDQ2NjAyMg/index.html>

The Predicted Planetary A Index for November 8 to 14 is 25, 18, 12, 10, 
5, 5, 5 with a mean of 11.4. Predicted Planetary K Index is 5, 4, 4, 3, 
2, 2, 2 with a mean of 3.1. 10.7 centimeter flux 135, 135, 132, 140, 
140, 145, 145 with a mean of 138.8.

For more information concerning shortwave radio propagation, see 
www.arrl.org/propagation 
<https://arrl.informz.net/z/cjUucD9taT0zNDgzNDg1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDQ2NjAyMw/index.html> 
and the ARRL Technical Information Service web page at 
www.arrl.org/propagation-of-rf-signals 
<https://arrl.informz.net/z/cjUucD9taT0zNDgzNDg1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDQ2NjAyNA/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/cjUucD9taT0zNDgzNDg1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDQ2NjAyNQ/index.html>. 
Information and tutorials on propagation can be found at http://k9la.us 
<https://arrl.informz.net/z/cjUucD9taT0zNDgzNDg1JnA9MSZ1PTUyNTQ3MzY2NCZsaT00MDQ2NjAyNg/index.html>.

NNNN

/EX

	

	

	

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