SB PROP @ ARL $ARLP013
ARLP013 Propagation de K7RA

ZCZC AP13
QST de W1AW 
Propagation Forecast Bulletin 13 ARLP013
From Tad Cook, K7RA
Seattle, WA March 31, 2023
To all radio amateurs 

SB PROP ARL ARLP013
ARLP013 Propagation de K7RA

Solar activity increased this week. Average daily sunspot number
rose from 68 to 112.6, and average daily solar flux changed from
145.6 to 156.1.

A new sunspot group emerged on March 24, two more on March 26 and
27, and three on March 29.

Due to solar wind and a geomagnetic disturbance at the beginning of
the reporting week, average daily planetary A index increased from
10.6 to 23.3, while average middle latitude A index went from 8.4 to
13.7. Many reports of aurora came in this week, some down to lower
latitudes in North America.

Predicted solar flux is 135 on March 31, 130 on April 1-6, 132 on
April 7-8, then 130, 132, 135 and 135 on April 9-12, then 140, 145
and 148 on April 13-15, then 150, 150, 155, 155 and 158 on April
16-20, 160 on April 21-23, then 155, 145 and 145 on April 24-26, and
135 on April 27 through May 1, then 132 on May 2-5, then 130, 132,
135 and 135 on May 6-9.

Predicted planetary A index is 18, 16, 12, 10 and 8 on March 31
through April 4, then 5 on April 5-9, then 15, 12, 8 and 5 on April
10-13, 8 on April 14-15, then 12, 20, 15 and 5 on April 16-19, then
20, 15 and 10 on April 20-22, 8 on April 23-24, 5 on April 25-26,
then 12, 15, 10 and 8 on April 27-30, and 5 on May 1-6, then 15, 12
and 8 on May 7-9.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - March 30, 2023 from OK1HH.

"The strong geomagnetic storm on 23-24 March was not expected.
Moreover, it was classified as a G4, making it the most intense in
almost 6 years. The source of the solar wind was not identified with
certainty, but a large coronal hole in the south, near the central
meridian, could not be missed.

"As a consequence of the disturbance, the ionosphere first
experienced a rise in the critical frequencies of the F2 layer on 23
March, followed by a significant drop on 24-25 March. Their normal
values started to be registered again only after 26 March.

"Energetic flares are a reliable indicator of the increase in solar
activity. On March 29, the seventh X-class flare of the year was
registered. Yet a total of seven were registered in 2022 and only
two in 2021.

"Most of the sunspots are now on the western half of the solar disk.
As they gradually set, total solar activity will first decrease over
the next week before rising again."

Here are articles about solar activity as an existential threat:

https://bit.ly/3M28RQv

https://bit.ly/42W7xo4

https://bit.ly/40Qf6Lc

Nice sunspot video, before the aurora:

https://bit.ly/3K2alHX

AA7FV wrote on March 25:

"There was a 6-meter opening from Arizona to VK on March 24. I
received VK7HH in Tasmania at 2028 UTC on WSPR; he was using just
0.2 watts (200 mW)."

VK7HH responded:

"Yes, that WSPR spot was from my remote station running 200 mW from
a Zacktek WSPR TX into a 1/2 wave vertical antenna. HASL 931m."

AA7FV wrote:

"For reference, my 50 MHz antenna is a Cushcraft 1/2-wave vertical,
the Ringo AR6, with its base at about 10 feet above ground. The
location here is 870m asl but I'm in the valley, just outside
Tucson. The receiver is an ancient Icom PCR1000, but with a preamp.
I monitor 6m 24/7, but rarely hear any signals at all, and when I do
hear something it's usually from someone else in Arizona."

On March 25, Jon, N0JK wrote:

"Worked VP8NO in GD18 today on 6 Meter FT8 at 1905 UTC. de N0JK
EM28 in Kansas."

Jon was using a portable 2 element Yagi and running 50 watts.

Here is an article about a "Hole" in the Sun:

https://www.space.com/solar-flare-coronal-hole-space-weather

Send your tips, reports, observations, questions and comments to
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
http://www.arrl.org/propagation and the ARRL Technical Information
Service 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/ .

Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins .

Sunspot numbers for March 23 through 29, 2023 were 73, 108, 105,
125, 128, 114, and 135, with a mean of 112.6. 10.7 cm flux was 151,
157.5, 160.3, 159.4, 158.2, 158.7, and 147.8, with a mean of 156.1.
Estimated planetary A indices were 60, 66, 15, 8, 3, 5, and 6, with
a mean of 23.3. Middle latitude A index was 28, 40, 12, 6, 2, 4, and
4, with a mean of 13.7.
NNNN