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SB PROP @ ARL
$ARLP004
ARLP004
Propagation
Update
ZCZC
AP04
QST
de W1AW
Propagation
Forecast
Bulletin 4
ARLP004
From
ARRL
Headquarters
Newington
CT February 7,
2025
To
all radio
amateurs
SB
PROP ARL
ARLP004
ARLP004
Propagation
Update
Spaceweather.com
reports that
sunspot 3981
has produced
more than 20
M-class
solar flares,
including two
that almost
reached
category X.
The
activity is
likely to
continue
today. The
sunspot
retains a
delta-class
magnetic field
that harbors
energy for
frequent
explosions.
The
current solar
forecast calls
for there to
be no G1
(Minor) or
greater
geomagnetic
storms. A
potential
glancing blow
is possible on
February 7 and
8.
Solar
radiation - as
observed by
NOAA GOES-18
over the past
24 hours - was
below the
S-scale storm
level
thresholds.
(The S-scale
is used to
indicate the
severity of
energetic
particles
emitted from
the Sun.) The
scale ranges
from S1
(minor) to S5
(extreme).
There is a
chance for S1
(Minor) or
greater solar
radiation
storms due to
the complex
cluster of
sunspot groups
in the
Northwest
Quadrant of
the Sun.
Radio
Blackouts are
expected
through
February 8,
with a chance
for R3
(Strong)
events due to
several
magnetically
complex
sunspot
groups.
There
is a chance
for S1 (Minor)
or greater
solar
radiation
storms through
February 9 as
the complex
cluster of
sunspot
regions in the
north
continues to
rotate closer
to the western
limb.
The
geomagnetic
field activity
is expected to
be unsettled
to active
levels on
February 10 to
19.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere,
February 6,
2025, from F.
K. Janda,
OK1HH:
"The
current
11-year solar
cycle
beautifully
shows how
little we
still know
about the
universe we
live in.
Including the
Sun, which is
a relatively
very stable
star
(otherwise we
wouldn't be
here). Each
'eleven year'
cycle is
different from
all the
previous ones,
and
all previous
attempts to
predict the
next one have
always failed.
Better said -
some of them
have proven to
be valid. But
only some.
"The
current
developments
do not appear
to be complex.
Coronal holes
11 and 12 were
followed by
the somewhat
surprisingly
active regions
of AR3976 -
3971, where
eruptive
activity rose
and fell
irregularly.
Occasionally
including
CMEs, which
although they
mostly did not
hit the Earth,
sometimes
partially did.
"The
ionospheric
shortwave
propagation
conditions
were therefore
mostly above
average, but
at the same
time very
variable.
There was no
way to
accurately
predict their
course, even
if only for
the next
24
hours. On the
other hand,
there was no
major
disturbance
that would
have made them
significantly
worse. There
is only one
thing to say
about the
future
development:
it will be
relatively
easy to
predict at
first sight.
But only at
first sight,
the reality
will probably
be more
different than
usual."
For
more
information
concerning
shortwave
radio
propagation,
see www.arrl.org/propagation
and the ARRL
Technical
Information
Service web
page 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
located at,
arrl.org/w1aw-bulletins-archive-propagation.
Check
out this QST
article about
Solar Indices:
https://bit.ly/3Rc8Njt
The
predicted
Planetary A
index for the
period
February 9 to
14 is 5, 10,
15, 15, 20,
and 10. The
predicted
largest Kp
index is 2, 3,
3, 4, 5, and
3. Predicted
10.7 cm flux
is 200, 200,
195, 195, 195,
and 190.
NNNN
/EX
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