SB PROP @ ARL $ARLP001
ARLP001 Propagation de K7RA
QST de W1AW
Propagation Forecast Bulletin 1 ARLP001
From Tad Cook, K7RA
Seattle, WA January 6, 2023
To all radio amateurs
SB PROP ARL ARLP001
ARLP001 Propagation de K7RA
Two new sunspot groups emerged on December 29, one more on December
30 and another on January 1, then two more on January 5.
Solar activity was a little higher, with average daily sunspot
number rising from 96.1 to 97, and solar flux averages rose 14
points to 157.8.
On Thursday, January 5 the sunspot number rose to 103, above the
average of 96.1 over the previous seven days.
Predicted solar flux is 154 on January 6, 152 on January 7-8, 150 on
January 9, 148 on January 10-11, then 146, 148 and 145 on January
12-14, 140 on January 15-16, 145 on January 17-19, 150 and 155 on
January 20-21, 160 on January 22-23, 165 on January 24-26, then 160,
155, 155, 158 and 155 on January 27-31, 150 and 148 on February 1-2,
145 on February 3-4, 140 on February 5-6, 150 on February 7-9, 145
on February 10, 140 on February 11-12, and 145 on February 13-15.
Predicted planetary A index is 12 and 8 on January 6-7, 5 on January
8-16, then 8, 12, 25, 20 and 10 on January 17-21, 5 on January
22-24, then 8, 28, 15 and 10 on January 25-28, and 5 on January
29-30, 18 on January 31 through February 1,15 and 10 on February
2-3, and 5 on February 4-12.
"Solar activity increased so rapidly in recent years that earlier
last year it already reached the level predicted for July 2025, the
predicted peak of the current 25th solar cycle. The year 2022 ended
with the highest monthly sunspot count in 7 years.
"Solar flares are already routinely of moderate magnitude (M-class
in X-rays), while geomagnetic disturbances are so far only very
rarely in a higher class than G1 (minor). In the G1 class was also
the disturbance on 30 December, which was triggered by a CIR
(co-rotating interaction region) impact, as predicted.
"This week the Earth is in the impact zone of possible eruptions in
the AR3176 sunspot group directly opposite our planet, which
produces M-class solar flares. The strongest so far, on December 30
at 1938 UTC, was class M3.7, which sent a CME toward Earth with an
expected arrival on January 4 - and the prediction proved correct -
the disturbance began at 0254 UTC.
"The CMEs filled the space between the Sun and Earth, and clouds of
solar plasma shielded the incoming cosmic rays enough to reach a
"Thus, since 26 December, we can observe the 'Forbush Decline,'
named after the American physicist Scott Forbush, who studied cosmic
rays in the early 20th century and first noticed the relationship
between them and solar activity. With more CMEs hitting Earth, the
cosmic ray decline will grow.
"On January 3 at 1058 UTC, something exploded on the far side of the
Sun. The Solar and Heliospheric Observatory (SOHO) detected a bright
CME sweeping across the southeastern limb of the Sun. The source of
the outburst was likely the old sunspot AR3163, which has been on
the Sun's far side for the past two weeks. We are now starting to
see it on the solar disk as AR3182, and we might tentatively expect
an X-class flare from it.
"The Geminid meteor shower is coming to Earth these days. On the
first three days of January, the most meteors arrived on January 3
at 2127 UTC when the Zenithal Hourly Rate (ZHR) of 125.3 was
calculated. Also, the activity of the sporadic-E layer in the
ionosphere increased, which we immediately noticed in the fading
shortwave propagation conditions (because sporadic-E is sporadic).
"ZHR (Zenithal Hourly Rate) of a meteor shower is the number of
meteors a single observer would see in an hour of peak activity if
it was at the zenith, assuming the observing conditions are
excellent (when and where stars with apparent magnitudes up to 6.5
are visible to the naked eye)."
OK1HH mentioned sunspot numbers are ahead of the consensus forecast
for Solar Cycle 25, so we will compare averages from a year ago with
In Propagation Forecast Bulletin ARLP001 for 2022, the average
sunspot number reported was 36.4, and 97 in the current report.
Average solar flux a year ago was 91.4, compared to 157.8 this week.
Reader David Moore sends along this link about our Sun's corona:
Here is an article on Siberian Radioheliograph:
A record of old sunspot numbers can be found here:
Solar Terrestrial Activity Report:
Identifying unknown HF signals:
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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
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/ .
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bulletins are at http://arrl.org/bulletins .
Sunspot numbers for December 29, 2022 through January 4, 2023 were
113, 121, 82, 94, 94, 89, and 86, with a mean of 97. 10.7 cm flux
was 162.8, 178.3, 164.9, 152.6, 146.4, 148.5, and 151, with a mean
of 157.8. Estimated planetary A indices were 11, 31, 16, 14, 8, 7,
and 21, with a mean of 15.4. Middle latitude A index was 8, 22, 10,
9, 5, 5, and 17, with a mean of 10.9.