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SB PROP @ ARL
$ARLP026
ARLP026
Propagation
Forecast
ZCZC AP26
QST de W1AW
Propagation
Forecast
Bulletin 26
ARLP026
From ARRL
Headquarters
Newington, CT
June 26, 2026
To all radio
amateurs
SB PROP ARL
ARLP026
ARLP026 The
ARRL Solar
Report
Solar activity
has remained
at low levels,
with frequent
C-level
activity in
the SE
quadrant of
the solar
disk.
The largest
flare of the
period was a
C3.8 on June
24 from Region
4478, which is
the large
sunspot that
Solar Orbiter
had been
tracking
across the Sun
ís far side.
While the
majority of
the flaring
activity this
period came
from 4478,
Region 4475
also produced
several small
C-flares as
additional
trailing spots
began to
emerge.
Regions 4472
and 4473
continued to
decay
throughout the
period.
Region 4479
was numbered
this period.
No
Earth-directed
CMEs were
observed in
available
coronagraph
imagery.
Solar activity
is expected to
continue at
predominately
low levels on
June 25 to 27
with a high
chance for
M-flares
(R1-R2/minor-moderate)
and a slight
chance for
X-flares
(R3/strong),
primarily due
to the
potential of
Region 4478.
Solar wind
parameters
were elevated
this period
from a mix of
negative
polarity
coronal hole
high speed
stream (CH
HSS) onset and
minor magnetic
transient
influences.
The solar wind
speed began
the period
averaging 350
km/s, then
increased
sharply on
June 24 to
~450 km/s.
This was
followed by
another
notable jump
in speed, also
beginning June
24, ending the
reporting
period at
approximately
600 km/s. Phi
was
predominantly
negative
(towards the
Sun). Solar
wind
conditions are
expected
remain
elevated/disturbed
through June
27 due to the
continued
influence of
the negative
polarity
coronal hole
high speed
stream.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere
June 26 by
F.K. Janda,
OK1HH: After
the last and
largest
sunspot group
in the chain
as observed by
the Solar
Orbiter
appeared on
the
southeastern
limb of the
solar disk, we
can expect
another
increase in
solar activity
to a level
somewhat
higher than
expected.
At the same
time, there
are three
coronal holes
near the
central
meridian, with
additional
active regions
just ahead of
them.
As a result,
the solar wind
intensified
significantly
on June 24,
triggering a
geomagnetic
disturbance.
The maximum
southern
(i.e.,
longitudinal)
component of
Bz reached -12
nT, whereas
this trend
appears set to
continue
through June
27. This will
result in
highly
variable
shortwave
propagation
conditions.
Furthermore,
propagation
will be more
affected by
the sporadic E
layer than in
recent days.
The Predicted
Planetary A
Index for June
27 to July 3
is 8, 5, 5, 5,
5, 5, and 18
with a mean of
7.3. The
Predicted
Planetary K
Index is 3, 2,
2, 2, 2, 2,
and 5 with a
mean of 2.6.
10.7
centimeter
flux is 130,
130, 132, 135,
145, 138, and
140 with a
mean of 135.7.
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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