01/17/2025

Sorry to say this is the last ARRL Propagation Forecast Bulletin I
will write.ÿ I took over in 1991 from Ed Tilton, W1HDQ when he was
too ill and weak to continue, and now with ALS I have similar
problems.

Geomagnetic influencers were more stable this week (planetary A
index shifted from 16.9 to 10.7) and solar indicators were weaker.
Average daily sunspot number changed from 159.1 to 103.3 and average
daily solar flux from 184.3 to 161.9.

Predicted activity indicates solar flux at 210 on January 17-18, 215
on January 19, 220 on January 20-21, 215 on January 22, 220 on
January 23-24, 170 on January 25-26, 175 on January 27-28, 170 on
January 29-30, then 165 and 160 on January 31 through February 1,
155 on February 2-3, 150 on February 4-6, 145 on February 7-8, 150
on February 9, 145 on February 10-12, 150 on February 13, 155 on
February 14-15, 160 on February 16, and 165 on February 17-20.

The forecast for planetary A index is 15, 12 and 8 on January 17-19,
8 on January 20-21, 5 on January 22-30, then 20 on January 31
through February 2, then 15, 12, 12 and 10 on February 3-6, then 5
on February 7-9, 8 on February 19-11, 5 on February 12, 8 on
February 13-16 and 5 on February 17-26.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere, January 16, 2025, from F. K. Janda, OK1HH:

"There is no indication that the prediction of an upsurge in solar
activity starting in mid-January will come to pass. The development
is quieter, with no major solar flares occurring. The sunspot groups
that are currently observable from Earth have stable magnetic
fields. More important flares are therefore rather unlikely.

"The geomagnetic field, while not calm, is not disturbed. Intervals
of quiescence alternate irregularly with slight upswings in
activity. Ionospheric shortwave propagation conditions are therefore
not as good as we had hoped based on the predicted rise in solar
activity, but they are not bad either. This type of development is
likely to continue."

The latest from the Royal Observatory of Belgium:

https://www.sidc.be[1]

For more information concerning shortwave radio propagation, see http://www.arrl.org/propagation[2] and the ARRL Technical Information
Service web page at, http://arrl.org/propagation-of-rf-signals[3]. For
an explanation of numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere[4] .

An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation[5] . More good
information and tutorials on propagation are at http://k9la.us/[6] .

Also, check this QST article:

https://bit.ly/3Rc8Njt[7]

"Understanding Solar Indices" from September 2002 QST.

Instructions for starting or ending email subscriptions to ARRL
bulletins are at http://arrl.org/bulletins[8] .

Sunspot numbers for January 9 through 15, 2025 were 126, 105, 85,
99, 100, 106, and 102 with a mean of 103.3. 10.7 cm flux was 162.2,
156.9, 156, 158.4, 159.7, 166.4, and 173.5 with a mean of 161.9.
Planetary A index was 10, 12, 7, 7, 11, 12 and 16, with an average
of 10.7. Middle latitude A Index was 9, 11, 5, 6, 9, 10, and 11,
with a mean of 8.7.

ÿ


[1] https://www.sidc.be
[2] http://www.arrl.org/propagation
[3] http://arrl.org/propagation-of-rf-signals
[4] http://arrl.org/the-sun-the-earth-the-ionosphere
[5] http://arrl.org/w1aw-bulletins-archive-propagation
[6] http://k9la.us/
[7] https://bit.ly/3Rc8Njt
[8] http://arrl.org/bulletins

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