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SB PROP @ ARL
$ARLP041
ARLP041 The
ARRL Solar
Report
ZCZC AP41
QST de W1AW
Propagation
Forecast
Bulletin 41
ARLP041
From ARRL
Headquarters
Newington CT,
October 31,
2025
To all radio
amateurs
SB PROP ARL
ARLP041
ARLP041 The
ARRL Solar
Report
Solar activity
has decreased
to very low
levels.
Region 4266
exhibited
signs of
slight
development as
it gained
asymmetric
penumbra
surrounding
its trailing
spots.
Meanwhile,
Region 4267
underwent
decay, losing
several
leading spots.
Additional
activity
included a
coronal mass
ejection (CME)
off the NE
limb on
October 29.
An associated
Type II radio
sweep was
reported with
the CME;
however, SUVI
195 imagery
revealed the
CME to have
originated on
the far side.
Also, an
approximate
12-degree
filament
eruption,
centered near
N27W24, was
observed
becoming
unstable
beginning on
October 29.
Most of the
material of
this event
appeared to
have been
reabsorbed,
with perhaps a
faint and
narrow CME
escaping.
Modeling of
this event
revealed a
possible
glancing blow
to the north
of Earth by
late on
November 2,
but confidence
is low in both
the analysis
of this event
and the
modeling
outcome.
Solar wind
parameters
continued to
reflect
positive
polarity
coronal hole
high-speed
stream (CH
HSS)
influences.
Solar wind
parameters are
expected to
continue to
reflect
positive CH
HSS influences
through
November 1.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere,
October 30,
2025, by F. K.
Janda, OK1HH:
"It is very
rare for the
situation on
the Sun and
between it and
Earth to be as
relatively
simple and
clear as it
has been in
recent days.
This is one of
the reasons
why it was
possible to
make a fairly
accurate
prediction of
further
developments.
Although there
were concerns
that an
intensified
solar wind
could hit
Earth as early
as October 26,
the original
forecast
ultimately
proved
accurate, and
the
disturbance
began on
October 28.
The last
weekend in
October was
thus marked by
relatively
good
conditions for
radio wave
propagation on
all shortwave
bands.
"Regular
helioseismological
observations
of the far
side of the
Sun are
closely
monitoring the
only two
currently
active regions
on the Sun.
They will
begin to
emerge on the
eastern edge
of the solar
disk in the
first half of
next week,
which will
immediately be
reflected in
an increase in
solar flux.
This may peak
around October
10, but it
seems that it
will happen
sooner.
"The increase
in solar
activity
during the
usual
favorable
seasonal
changes alone
will result in
improved
conditions for
shortwave
propagation.
With a little
luck, the
improvement
could peak
around
November 8,
when the next
increase in
geomagnetic
activity can
be expected."
Solar activity
is expected to
be at moderate
levels until
November 15
due to the
return of
Region 4246.
Low levels are
expected to
prevail from
November 14 to
22 as multiple
regions depart
the visible
disk.
A greater than
2 MeV electron
flux at
geosynchronous
orbit is
expected to be
at high levels
until November
15 due to
responses from
recurrent CH
HSS
influences.
Moderate
levels are
expected from
November 16 to
22.
Geomagnetic
field activity
is expected to
be at quiet to
unsettled
levels on
November 1 to
6, 10 to 14,
and November
16 to 22.
Active
conditions are
expected from
November 7 to
9 and November
15.
The latest
video report
from Dr.
Tamitha Skov,
WX6SWW, can be
found on
YouTube at https://www.youtube.com/watch?v=y8uEPcivbQ8.
Spaceweather.com for October 31 reports on "Halloween Fireballs" and the
rapid
brightening of
Comet
3I/ATLAS.
The Predicted
Planetary A
Index for
November 1 to
7 is 8, 5, 5,
5, 5, 5, 8,
and 12, with a
mean of 6.9.
Predicted
Planetary K
Index is 3, 2,
2, 2, 2, 3,
and 4, with a
mean of 2.6.
10.7-centimeter
flux is 130,
130, 135, 140,
140, 140, and
140, with a
mean of 136.4.
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.
Information
and tutorials
on propagation
can be found
at http://k9la.us.
NNNN
/EX
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