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SB PROP @ ARL
$ARLP002
ARLP002
Propagation de
K7RA
ZCZC
AP02
QST
de W1AW
Propagation
Forecast
Bulletin 2
ARLP002
From
Tad Cook, K7RA
Seattle,
WA January 10,
2025
To
all radio
amateurs
SB
PROP ARL
ARLP002
ARLP002
Propagation de
K7RA
Solar
activity was a
bit weak
during recent
days. Average
daily sunspot
number was
159.1. During
the previous
week the
average was
194.7.
Predicted
solar flux for
the near term
is 165 on
January 10-11,
160 on January
12, 155 on
January 13-17,
200, 210 and
220 on January
18-20, then
230 on January
21-25, then
225, 220, 215,
210, 205 and
200 on January
26-31, 170 on
February 1-2,
165 on
February 3-4,
170 on
February 5-6
and 175 on
February 7.
Predicted
planetary A
index is 8 on
January 10-11,
then 10 on
January 12-13,
5 on January
13-14, then 8
on January
15-16, 10 on
January 17-20
and 5 on
January 21-30,
then 18, 15,
12, 10 and 8
on January 31
through
February 4.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere -
January 9,
2025, from F.
K. Janda,
OK1HH:
"For
most of the
eleven-year
solar cycle,
two numbers
are more or
less
sufficient to
give us a
rough estimate
of the state
of the
ionosphere and
shortwave
propagation
conditions:
the solar
activity index
(optimally the
solar flux)
and the
geomagnetic
activity index
(usually the
daily A index
or the
three-hour K
index is
sufficient).
We need more
information
during the
high solar
activity
period and
much more at
the peak of
the high
cycle.
"It
may not yet be
enough to
understand
what is going
on, let alone
predict it.
These include
the solar wind
speed and
particle
density (free
electrons and
especially
energetic
protons) and
the strength
and polarity
of the
longitudinal
component of
the
interplanetary
magnetic
field. Another
excellent tool
is ionospheric
probe
measurements,
especially
ionograms.
Unlike the
pre-Internet
era, we all
have access to
them.
"Yet, or
perhaps
because of
this, we often
experience
surprises,
whether a lull
or
disturbance.
The quiet
post-Christmas
period and the
big solar
flares on 30
December were
followed by
geomagnetic
disturbances
on 1-2
January,
accompanied by
auroras and
SAR,
observable
even in the
mid-latitudes.
The following
decrease in
solar activity
and irregular
rises in
geomagnetic
activity (3-7
January)
mostly
resulted in a
deterioration
of shortwave
conditions.
The
improvements
were mostly
brief and
occurred
irregularly.
Moreover,
forecasts of
further
developments
were
unreliable.
"A
further
upsurge in
solar activity
is not
expected until
the second
half of
January, after
large sunspot
groups begin
to reappear in
the eastern
part of solar
disk. With few
exceptions,
major
geomagnetic
disturbances
should follow
after the
active regions
on the Sun
reach the
central
meridian, in
February."
"Solar
Observances"
from the Royal
Observatory of
Belgium: https://www.sidc.be
For
more
information
concerning
shortwave
radio
propagation,
see www.arrl.org/propagation
and the ARRL
Technical
Information
Service web
page at, www.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.
An
archive of
past
propagation
bulletins is
at www.arrl.org/w1aw-bulletins-archive-propagation.
More good
information
and tutorials
on propagation
are at http://k9la.us.
Also,
check this
article:
"Understanding
Solar Indices"
from September
2002 QST.
https://bit.ly/3Rc8Njt
Instructions
for starting
or
ending email
subscriptions
to ARRL
bulletins are
at www.arrl.org/bulletins.
Sunspot
numbers for
January 2
through 8,
2025 were 173,
190, 193, 178,
154, 113, and
113 with a
mean of 159.1.
10.7 cm flux
was 212.4,
199.9, 209.3,
168.6, 171.9,
167.7,and
160.2 with a
mean of 184.3.
Planetary A
index was 22,
9, 32, 20, 12,
15 and 8 with
an average of
16.9. Middle
latitude A
Index was 14,
7, 21, 12, 13,
8, and 6, with
a mean of
11.6.
NNNN
/EX
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