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SB PROP @ ARL
$ARLP014
ARLP014
Propagation
Forecast
ZCZC AP14
QST de W1AW
Propagation
Forecast
Bulletin 14
ARLP014
From ARRL
Headquarters
Newington, CT
April 3, 2026
To all radio
amateurs
SB PROP ARL
ARLP014
ARLP014 The
ARRL Solar
Report
Solar activity
has been at
low levels
with only
C-class flares
produced by
Regions 4401,
4405, and
4409. There
were 9
numbered
active regions
on the solar
disk, with
4409 showing
the most
significant
growth during
the period and
producing the
largest flares
on April 1. A
new region
emerged, but
it has not yet
been numbered.
Multiple
filaments
erupted during
the day on
April 1,
producing
coronal mass
ejections
(CMEs)
observed in
coronagraph
imagery, but
their
propagation
modeling did
not suggest
impacts to
Earth.
The exceptions
are the ejecta
first observed
at GONG
H-alpha images
on April 1.
Solar activity
is likely to
reach moderate
(R1/R2-minor/moderate) levels, with a slight chance for X-class
(R3-strong)
flares through
April 4, due
primarily to
the flare
potential of
Regions 4404,
4405, and
4409.
Solar wind
parameters
were near
nominal levels
with solar
wind speed
averaging
around 440
km/s.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere,
April 2, 2026,
by F. K.
Janda, OK1HH:
The increase
in overall
solar activity
during the
third ten-day
period of
March, albeit
with a slight
delay, led to
a gradual rise
in MUF values,
extending into
the first days
of April.
An increase in
solar flare
activity did
not occur
until April
30, beginning
with a flare
at 0319 UT
with an X-ray
intensity of
X1.4, which
lasted a long
time and was
accompanied by
a CME.
Since a large
coronal hole
No.
36 was located
nearby, a
significant
increase in
geomagnetic
activity was
expected.
This did not
occur until
April 2, but
already during
several
preceding
active
intervals, we
could observe
the effects of
electromagnetic wave scattering on ionospheric inhomogeneities, clearly
visible even
on ionograms.
Active region
NOAA 4405,
located 27
degrees south
of the solar
equator, has
been clearly
visible for a
week as the
largest on the
solar disk and
appears to be
stable.
On April 3, it
passes the
central
meridian, and
its proximity
to coronal
hole No.
36 is a
potential
source of
intensified
solar wind.
It also
indicates
higher
geomagnetic
activity (at
G2 level since
April 2). This
proximity will
likely be the
cause of
increased
geomagnetic
activity
during the
first ten days
of April.
Consequently,
this will lead
to irregular
shortwave
propagation
conditions and
more frequent
drops in the
MUF.
The next
increase in
solar activity
will likely
occur in the
last third of
April.
Daily MUF
values will
rise again,
and at the
same time, a
sporadic E
layer will
begin to
appear
occasionally
in
mid-latitudes.
Although it
will not yet
have a
significant
impact on
shortwave
propagation,
it will
occasionally
cause
interesting DX
openings on
the shortest
shortwave
bands.
The Predicted
Planetary A
Index for
April 4 to
April 10 is
22, 10, 15, 8,
7, 25, and 40
with a mean of
18.1. The
Predicted
Planetary K
Index is 5, 3,
4, 3, 2, 5,
and 6 with a
mean of 4.
145, 145, 135,
125, 118, 120,
and 110 with a
mean of 128.2
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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