(C) ARRL Letter
This story was originally published by ARRL Letter and is unaltered.
. . . . . . . . . .
The K7RA Solar Update [1]
[]
Date: 2025-01
Currently a geomagnetic storm is raging. On January 1-2, Alaska's
college A index reached 113.
Predicted planetary A index is 12 on January 3, then 18, 18, 12, 10
and 8 on January 4-8, 5 on January 9-10, 10 and 8 on January 11-12,
5 on January 13-15, 12 on January 16, 10 on January 17-20, 5 on
January 21-25, then 8, 50, 20 and 8 January 26-29.
Predicted solar flux is 215 on January 3-4, then 205, 210, 205 and
205 on January 5-8, then 200, 170 and 165 on January 9-11, 170 on
January 12-13, 175 on January 14-15, 180, 190, 200, 210 and 220 on
January 16-20, 230 on January 21-25, 240 on January 26-27, then 220,
200 and 195 on January 28-30.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - January 2, 2025, from OK1HH:
"Considering the high solar flare activity, there was a relatively
high probability of an increase in geomagnetic activity during the
Christmas holidays.
"But currents of enhanced solar wind avoided the Earth and therefore
it was surprisingly quiet for a relatively long period from
Christmas almost until the end of the year, more precisely from 25
to 30 December.
"Strong solar flares in the last two days of December were followed
by CMEs that were at least partially directed towards the Earth.
This prompted all geomagnetic field activity forecasters to jointly
and indiscriminately predict the occurrence of geomagnetic
disturbances and auroras for 31 December and 1 January.
"Particles ejected by the second of the major eruptions hit the
Earth more effectively. Therefore, the geomagnetic disturbance on 31
December was weaker. The major disturbance on January 1, 2025 was
accompanied by beautiful auroras.
"At first approximation, the unexpected development of ionospheric
shortwave propagation on New Year's Day may have seemed surprising.
Not only were they not bad, but their development was irregular,
while the MUF values were even above average. The cause can be found
also in the previous calm development (25 to 30 December) and also
in the fact that the solar wind speed started to increase gradually
only from 1 January.
"The most active regions on the Sun now fall behind the western limb
of the solar disk. Therefore, solar activity will slowly decrease.
But it will be sufficient to open all shortwave bands. At the same
time, the Earth's magnetic field activity will also be decreasing,
so the evolution of ionospheric propagation conditions should be
more stable, while remain mostly above average on most days."
An article from "yourweather.co.uk" regarding the solar max:
https://bit.ly/41ZnwUq
Latest video from Dr. Tamitha Skov, WX6SWW (Space Weather Woman):
https://youtu.be/k3gxVE74Xa0
For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation and the ARRL Technical Information
Service web page at,
http://arrl.org/propagation-of-rf-signals. For
an explanation of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere .
An archive of past propagation bulletins is at,
http://arrl.org/w1aw-bulletins-archive-propagation . More good
information and tutorials on propagation are at
http://k9la.us/ .
Also, check this:
https://bit.ly/3Rc8Njt
"Understanding Solar Indices" from September 2002 QST.
Instructions for starting or ending email subscriptions to ARRL
bulletins are at,
http://arrl.org/bulletins .
Sunspot numbers for December 26, 2024 through January 1, 2025 were
211, 233, 213, 209, 162, 172, and 163 with a mean of 194.7. 10.7 cm
flux was 255.8, 258.5, 260.3, 254.7, 223.5, 216.2, and 219.2 with a
mean of 241.2. Planetary A index was 3, 3, 4, 5, 7, 10 and 86 with
an average of 16.9. Middle latitude A Index was 3, 5, 7, 10, 7, 10,
and 48, with a mean of 12.9.
[END]
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[1] Url:
https://www.arrl.org/news/the-k7ra-solar-update-860
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