SB PROP @ ARL $ARLP011
ARLP011 Propagation de K7RA
ZCZC AP11
QST de W1AW
Propagation Forecast Bulletin 11 ARLP011
From Tad Cook, K7RA
Seattle, WA March 15, 2024
To all radio amateurs
SB PROP ARL ARLP011
ARLP011 Propagation de K7RA
Six new sunspot groups appeared over the past reporting week, March
7-13, and one more on March 14.
The first group emerged on March 7, two more appeared on March 12,
and three more on March 13.
Solar activity was down. Average daily sunspot number went from
106.7 to 82.3, and solar flux from 147.4 to 130.4. Geomagnetic
indicators were somewhat quieter, with average daily planetary A
index dropping from 10 to 8.9, and middle latitude A index from 8 to
7.
The Vernal Equinox in the Northern Hemisphere is on Wednesday, March
20 at 0306 UTC. This marks a transition to Spring HF conditions,
always a positive effect.
I am not certain where we are in Solar Cycle 25, perhaps near the
peak, or the max could be next year.
Solar activity seems to be in the doldrums recently, and of course
we will only know when the peak has occurred six to twelve months
after it happens. This is because the official smoothed sunspot
number is a one year average. This erases lots of noise in the
graphic representation due to daily variations in sunspot numbers.
The outlook for the next few weeks shows continued low numbers, with
predicted solar flux at 135 on March 15-17, then 140, 145, 150 and
155 on March 18-21, 135 on March 22-23, then 132, 130, 132 and 138
on March 24-27, 140 on March 28-29, then 142, 140, 135, 130 and 128
on March 30 through April 3, and 125 on April 4-8, then 122, 118,
122, 125, 122, 127 and 130 on April 9-15, then 135 on April 16-19.
Predicted planetary A index is 12, 8 and 8 March 15-17, 5 on March
18-27, then 10 and 8 on March 28-29, 5 on March 30 through April 2,
and 12 on April 3-5, then 5, 10, 8 and 8 on April 6-9, then 5 on
April 10-23.
"Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - March 14, 2024.
"In the last seven days, there were repeated situations where we
expected a CME to hit the Earth's magnetic field (while a weak G1
class geomagnetic storm was predicted by NOAA), but there have been
at most only isolated upswings, with the planetary K index at 4. The
active region AR3599 returned to the solar disk, but it was much
smaller and less active than during the last solar rotation. It
produced at least a strong M7.4 class solar flare on March 10 at
1213 UTC.
"Shortly after AR3599 sets behind the southwestern limb of the solar
disk, the former AR3590 rises in the northeast. According to
helioseismological observations, it remains the largest of all on
the Sun's far side. Its activity will have a decisive influence on
the evolution of shortwave propagation around the approaching
equinox.
"Thirty-five years ago, at the peak of Solar Cycle 22, a powerful
CME hit our planet. It happened on March 13, 1989, and within 90
seconds, the entire Hydro-Quebec power grid was knocked out. The
outage lasted nine hours, millions of Quebecois were without light
and heat, and nine months later, the affected area experienced a
significant increase in birth rates. The treachery consists in
inducing direct currents into the lines, to which the transformers
in the alternating current grid offer little resistance.
"On March 13, 1989, the biggest storm of the space age occurred. But
the bigger one was the 'Carrington Event' of September 1859. It
produced a storm twice as powerful as the one mentioned in March
1989. It later turned out that the cause was not one, but two CMEs,
and came from the X4.5 eruptions of March 10 and M7.3 of March 12.
"F. K. Janda, A.R.S. OK1HH."
NASA-funded team of scientists discovered long-lasting radio
signals:
https://bit.ly/48VrH3F
Sunspot cluster responsible for monster flare spotted on far side of
the Sun:
https://bit.ly/3IDA5Kc
Recent videos from Dr. Tamitha Skov, WX6SWW:
https://youtu.be/2nWLAYL01FA
https://youtu.be/v4wf-EjTN4k
Send your tips, reports, observations, questions, and comments to
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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 QST article about Solar Indices:
https://bit.ly/3Rc8Njt
Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins .
Sunspot numbers for March 7 through 13 2024 were 99, 91, 99, 77, 56,
68, and 86, with a mean of 82.3. 10.7 cm flux was 136.6, 129, 134.5,
127, 126.7, 130.5, and 128.3, with a mean of 130.4. Estimated
planetary A indices were 12, 11, 13, 7, 4, 6, and 9, with a mean of
8.9. Middle latitude A index was 8, 9, 11, 6, 4, 4, and 7, with a
mean of 7.
NNNN
/EX
