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://www.youtube.com/watch?v=Fx1goRRoBDg ]


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 [ 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 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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