QST de W1AW  
Propagation Forecast Bulletin 12  ARLP012
>From Tad Cook, K7RA
Seattle, WA  March 24, 2023
To all radio amateurs 

SB PROP ARL ARLP012
ARLP012 Propagation de K7RA

Sunspot numbers were lower again this week, with the average
declining from 143.6 two weeks ago to 118.7 last week and now 68
this week. Average daily solar flux sank 8 points from 153.6 last
week to 145.6.

Six new sunspot groups emerged over the week, one on March 17,
another March 18, three more on March 19, one more on March 21 and
another on March 22.

Predicted solar flux is 150, 145 and 145 on March 24-26, 150 on
March 27-28, 145 and 150 on March 29-30, 138 on March 31 through
April 1, then 136, 136 and 134 on April 2-4, 132 on April 5-7, 130
on April 8-9, then 132, 135, 138, and 140 on April 10-13, 142 on
April 14-15, 143 on April 16, 140 on April 17-18, 142 on April
19-21, and 144 on April 22, 146 on April 23-24, 142 and 140 on April
25-26, 138 on April 27-28, and 136 on April 29-30.

Predicted planetary A index is 35, 30, 20, 15 and 10 on March 24-28,
8 on March 29-30, then 18, 12, 12, 10 and 8 on March 31 through
April 5, 5 on April 6-9, then 15, 12, 8 and 5 on April 10-13, 8 on
April 14-15, then 12, 10, 5 and 5 on April 16-19, then geomagnetic
unrest returns with 10, 36, 20, 10, 8 and 5 April 20-25, then 20,
18, 12, 12 and 10 on April 26-30.

On Thursday, Spaceweather.com reported, 'The forecast did not call
for this. During the early hours of March 23rd, a crack opened in
Earth's magnetic field, and stayed open for more than 8 hours. Solar
wind poured through the gap to fuel a strong G3-class geomagnetic
storm.'

I watch this site frequently looking for disturbances when
propagation seems odd:

https://www.swpc.noaa.gov/products/planetary-k-index

On Thursday it showed estimated planetary K index at 7, then
dipping, and at 2100 UTC above 7. I noticed some very odd
propagation. At 1900 UTC I called CQ on 10 meter FT8, and
pskreporter.info showed I was only being heard in a small area in
east Texas. Stations were concentrated between 1739 and 1892 miles
in an area between Houston, San Antonio, Killeen and Nacogdoches.
That was it! Heard nowhere else. I was running low power, using a
simple end-fed one wavelength wire that is mostly indoors.

Over the next half hour coverage extended east to Louisiana, then
Alabama, then Georgia and South Caroline.

At 1950 UTC I went to 15 meters, and noticed a similar oddity, this
time with stations in an arc between 1510-2680 miles, bordered by
N1AC in Florida, NT5EE in Texas, KI5WKB in Oklahoma and a station in
North Carolina.

A check again at 0050 UTC last night on 15 meter FT8 and
pskreporter.info showed for over and hour the only stations I was
receiving were two Cubans, and the only stations hearing me were in
an arc from Arizona to Alabama.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - March 23, 2023 from F.K. Janda, OK1HH.

'If we were to assess solar activity in the last seven days by the
number and size of sunspots, or by the number of energetic flares,
it would not seem significant. Yet it was, but we only know that
because of satellite observations. For example, NASA's SDO
observatory recorded a dark plasma eruption at 0630 UTC on 17 March.

'The speed of the solar wind began to increase on 21 March. Far more
noticeable was a large coronal hole in the southern hemisphere of
the Sun near the central meridian. The assumption of a strong solar
plasma flow from its borders pointed to a probable disturbance on
March 24.

'But the flow was faster. We saw a really strong geomagnetic storm a
day earlier, on March 23. During the morning hours, the
concentration of free particles around the Earth began to rise
rapidly, as a reliable precursor of the coming storm. The
geomagnetic disturbance reached a planetary K index of 7 in the
afternoon, so its intensity was rated G3.

'Earth's ionosphere responded to the storm with an increase in MUF
during 23 March. Since the disturbance should continue, albeit with
less intensity, we expect initially below-average shortwave
propagation conditions and then a slow return to average.'

Another great video from Dr. Tamitha Skov, WX6SWW:

https://youtu.be/bG0zCbXukm4

This weekend is the CQ World-Wide SSB WPX Contest. See
https://cqwpx.com for info and rules. This is a big, fun contest in
which callsign prefixes are the multiplier.

Send your tips, reports, observations, questions and comments to
[email protected]. 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 and the ARRL Technical Information
Service at arrl.org/propagation-of-rf-signals . For an
explanation of numbers used in this bulletin, see
arrl.org/the-sun-the-earth-the-ionosphere .

An archive of past propagation bulletins is at
arrl.org/w1aw-bulletins-archive-propagation . More good
information and tutorials on propagation are at k9la.us/ .

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

Sunspot numbers for March 16 through 22, 2023 were 84, 58, 35, 73,
75, 70, and 81, with a mean of 68. 10.7 cm flux was 135.4, 134.2,
140.3, 142.7, 156.1, 151.6, and 158.9, with a mean of 145.6.
Estimated planetary A indices were 8, 7, 8, 10, 13, 8, and 17, with
a mean of 10.6. Middle latitude A index was 6, 7, 6, 8, 10, 8, and
14, with a mean of 8.4.