SB PROP @ ARL $ARLP031
ARLP031 Propagation de K7RA
ZCZC AP31
QST de W1AW
Propagation Forecast Bulletin 31 ARLP031
From Tad Cook, K7RA
Seattle, WA August 16, 2024
To all radio amateurs
SB PROP ARL ARLP031
ARLP031 Propagation de K7RA
With sunspot numbers and solar flux at times both above 300, recent daily
space weather has been exciting for radio amateurs who watch the sun. We like
higher activity because it correlates with a dense ionosphere, bringing with
it better conditions on higher
frequencies.
This extreme activity also comes with greater geomagnetic disturbance, which
cause higher absorption of HF signals.
For example, on August 12 the solar flux was 272.4 and sunspot number was
245. Middle latitude A index was 51 and planetary A index was 122, very high
values indicating the G4 geomagnetic storm.
Seven new sunspot groups appeared this week, two on August 8, four on August
11 and one on August 14.
On August 9 the daily sunspot number was 382, the highest in two decades.
Average daily sunspot numbers rose from 222.3 to 255, while average daily
solar flux increased from 255.3 to 284.9.
Average daily planetary A index went from 15.7 to 28.6, and average daily
middle latitude A index (measured at a single magnetometer in Virginia) from
13.4 to 17.9.
The solar flux outlook for the next few weeks looks promising, with values
peaking at 300 in the first week of September.
Predicted values from forecasters Jones and Kiser at the US Air Force are
230, 225 and 220 on August 16-18, 215 on August 19-20, then 210, 205, 200 and
210 on August 21-24, 220 on August 25-26, 235 on August 27-28, 245 on August
29-30, then 240, 245 and 270 on August 31 through September 2, 300 on
September 3-5, 290 on September 6-7, 280 on September 8, and 270 on September
9-11, then 260 on September 12-14, then 250, 240, 230, 210, 200 and 210 on
September 15-20, and 220 on September 21-22.
Predicted planetary A index is 10, 18, 30, 25 and 10 on August 16-20, then 5,
5 and 8 on August 21-23, then 5 on August 24 to September 17, then 18 and 12
on September 18-19, and 5 on September
10 until November.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere
for August 15, 2024 from F. K. Janda, OK1HH.
The current maximum of the "eleven-year" solar cycle is gradually surpassing
all expectations and all predictions. Medium-mass flares (M-class) are
observed almost daily and are often intense enough to silence radio signals
at least in the longer part of short waves by increasing the attenuation in
the lower ionosphere. Large solar flares (X-class) are no exception. They
usually (shortly) knock out the entire shortwave range.
Many eruptions are accompanied by a particle cloud ejection (CME). If this
happens near or west of the central meridian, it is very likely to "hit" the
globe and cause a geomagnetic disturbance. In the case of multiple particle
clouds flying toward the Earth at the same time, the first one may clear the
way for the following ones, causing an extremely strong disturbance. Which is
exactly what we saw on August 11-12.
The geomagnetic disturbance reached G4 level, while not only auroras were
observed in mid-latitudes during the disturbance, but also a phenomenon known
as STEVE (Strong Thermal Emission Velocity Enhancement), until relatively
recently confused with auroras. We observe it as a colored tilted ribbon.
Thanks to the simultaneous peak of the Perseids meteor shower, we were able
to witness a truly extraordinary spectacle.
The height of the highest critical frequencies of the f0F2 layer, and thus
the MUF, was on average at an eleven-year low of solar activity on August 12.
However, with the difference that as the radio wave passed through the
ionosphere, a large attenuation was produced, largely due to scattering on
inhomogeneities. The improvement in propagation conditions was slow and
gradual. A slightly better 13 August was followed by a deterioration on 14
August. Situation was only slightly above average on 15 August. But with that
said, we already knew of other CMEs heading towards Earth.
We don't expect a drop in solar activity anytime soon, if only because we
know of other active regions on the far side of the Sun thanks to
helioseismological observations. Soon we will be able to observe them on the
eastern edge of the solar disk.
W3LPL wrote in an email:
"Ain't this solar maximum great?
Solar Cycle 25 is now much, much stronger than anyone anticipated, and it s
slowly growing stronger through at least this weekend.
Today's Wednesday estimated international sunspot number is 281.
It s increasingly likely that we'll have widespread coast-to-coast and
worldwide 6 meter F2 propagation during about half of the days between late
October and at least early February.
Widespread F2 openings are likely to bring 6 meter CW and SSB to life like we
haven't experienced in more than 20 years.
The first sign of enhanced 6 meter F2 will be increasingly frequent TEP from
Europe and North America to South America and the South Atlantic islands. TEP
may begin very sporadically by late August and become increasingly frequent
later in September and especially during October.
Coast-to-coast F2 propagation and propagation crossing the Atlantic to Europe
and Africa may begin sporadically during September and October and become
frequent and long lasting by early November.
Effective 6 meter antennas can be very small.
3 element Yagis are small, lightweight and very effective. 20 foot antenna
height is adequate but sloping terrain or higher antennas perform much
better. Heights higher that 50 feet are not necessary and in many cases
perform poorly.
Are you ready for this once in a lifetime experience?"
I want to remind everyone of this useful web site:
https://prop.kc2g.com [
https://prop.kc2g.com/ ]
Record breaking number of sunspots:
https://www.space.com/sunspots-solar-cycle-25 [
https://www.space.com/sunspots-solar-cycle-25 ]
https://tinyurl.com/k9cnbtt8 [
https://tinyurl.com/k9cnbtt8 ]
Sky & Telescope:
https://tinyurl.com/musyznst [
https://tinyurl.com/musyznst]
Massive flare:
https://bit.ly/4fPW1Bp [
https://bit.ly/4fPW1Bp ]
Newsweek on aurora:
https://tinyurl.com/3wnckehs [
https://tinyurl.com/3wnckehs ]
Cycle 26:
https://tinyurl.com/3jdhyekc [
https://tinyurl.com/3jdhyekc ]
Forbes claims quarter century max:
https://tinyurl.com/yhm398ph [
https://tinyurl.com/yhm398ph ]
Red Deer, Alberta:
https://tinyurl.com/y5a7sv3f [
https://tinyurl.com/y5a7sv3f ]
Great solar image:
https://tinyurl.com/yc84azws [
https://tinyurl.com/yc84azws ]
New report from Tamitha Skov:
https://youtu.be/yd1gEZoYpsM [
https://youtu.be/yd1gEZoYpsM ]
Send your tips, reports, observations, questions and comments to
k7ra@arrl.net [ mailto:
k7ra@arrl.net ] . When reporting observations, don't
forget to tell us which mode you were operating.
For more information concerning shortwave radio propagation, see
www.arrl.org/propagation [
http://www.arrl.org/propagation ] 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 ] .
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/ [
http://k9la.us/ ] .
Also, check this:
https://bit.ly/3Rc8Njt [
https://bit.ly/3Rc8Njt ]
Instructions for starting or ending email subscriptions to ARRL bulletins are
at
www.arrl.org/bulletins [
http://arrl.org/bulletins ] .
Sunspot numbers for August 8 through 14 2024 were 337, 382, 234, 194, 245,
199, and 194, with a mean of 255. 10.7 cm flux was 336, 305.5, 291.1, 281.5,
272.4, 259.9, and 248.2, with a mean of 284.9. Estimated planetary A indices
were 7, 7, 7, 28, 122, 17, and 12, with a mean of 28.6. Middle latitude A
Index was 11, 9, 8, 23, 51, 12, and 11, with a mean of 17.9.
NNNN
/EX
ARRL The National Association for Amateur Radio®
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ARLP031 Propagation de K7RA