Subj : The K7RA Solar Update
To   : QST
From : ARRL de WD1CKS
Date : Fri Dec 13 2024 11:56 pm

12/13/2024

Average daily sunspot number plummeted to 104.4.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere for
December 12, 2024 from OK1HH:

"The high solar activity in October this year suggests that this may have been
the peak of an 11-year cycle.� This is not to say that solar activity will not
continue to rise.� On the contrary, it may well be that the first maximum of
the cycle took place in October and that we can look forward to a second
maximum.� This could take place in 2025 or 2026 at the latest, but it will be
followed by a decline.

"Solar activity in November was lower and December's is even lower. The
expected geomagnetic disturbance, predicted for 29 November, did not take place
because the CME did not affect the Earth.� However, the almost daily occurrence
of moderate solar flares continued and a large flare occurred.� It happened on
8 December at around 0906 UT. However, even after this eruption no major
geomagnetic disturbance followed and the changes in ionospheric shortwave
propagation were rather random."

In December, the Sun is quieter, and large sunspot groups do not occur in its
photosphere.� The only major active regions we see are to the south of the
solar equator, and their area is about half that of those seen in November.
However, the active area of AR3917 is slowly getting larger and with it the
likelihood of a larger flare is increasing.

The Earth's ionosphere has been repeatedly affected in recent days by increased
concentrations of solar-origin free electrons, which, while causing a slight
rise in MUF, have been more pronounced in the ionosphere, causing scattering
and hence attenuation, which has had a negative effect on the longer shortwave
bands.

More meteors are arriving at Earth these days.� The swarm is called the
Geminids and most meteors should arrive about December 14. Therefore we can
observe more frequent occurrences of the sporadic E layer.� In addition to the
occurrences of stronger signals on the longer shortwave bands, propagation
through ionospheric waveguides is more frequent.� The sporadic layer may not
only form one of the walls of the waveguide, but also enable its termination.
Which is a good chance, for example, for QRP devotees.

Predicted solar flux is 165 on December 13 to 15, 160 and 165 December 16 and
17, 160 on December 18 and 19, then 175, 185, and 190 on December 20 to 22, 185
on December 23 and 24, 180 on December 25 and 26, and 180 on December 30
through January 2, 2025.

Predicted planetary A index is 5 on January 13 and 14, 8 on January 15 and 16,
5 on January 17 to 20, then 8 on January 29.

Flare blasts South Africa:� https://bit.ly/3Do6nJJ[1]

STCE Newsletter Online version:

http://www.stce.be/newsletter/newsletter.php[2]

PDF version:

http://www.stce.be/newsletter/pdf/2024/STCEnews20241212.pdf[3]

Send your tips, reports, observations, questions and comments to
[email protected][4].� When reporting observations, don't forget to tell us which
mode you were operating. �

For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation[5] and the ARRL Technical Information Service
web page at http://arrl.org/propagation-of-rf-signals[6] .

�For an explanation of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere[7] .

An archive of past propagation bulletins is at

http://arrl.org/w1aw-bulletins-archive-propagation[8] .

More information and tutorials on propagation are at http://k9la.us/[9]

Check "Understanding Solar Indices" from September 2002 QST at
https://bit.ly/3Rc8Njt[10] .

Instructions for starting or ending email subscriptions to ARRL bulletins are
at http://arrl.org/bulletins[11] .

Sunspot numbers for December 5 through 11 2024 were 101, 103, 91, 103, 94, 125,
114, with a mean of 104.4.� 10.7 cm flux was 174.6, 177.5, 182.5, 177.7 172.5,
171.9, and 160.5 with a mean of 170.9. Estimated planetary A indices were 4, 8,
11, 7, 6, 13, and 7, with a mean of 8.� Middle latitude A Index was 3, 6, 9, 6,
6, 6, 10, and 5, with a mean of 7.3.� �


[1] https://bit.ly/3Do6nJJ
[2] http://www.stce.be/newsletter/newsletter.php
[3] http://www.stce.be/newsletter/pdf/2024/STCEnews20241212.pdf
[4] mailto:[email protected]
[5] http://www.arrl.org/propagation
[6] http://arrl.org/propagation-of-rf-signals
[7] http://arrl.org/the-sun-the-earth-the-ionosphere
[8] http://arrl.org/w1aw-bulletins-archive-propagation
[9] http://k9la.us/
[10] https://bit.ly/3Rc8Njt
[11] http://arrl.org/bulletins

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