|
SB PROP @ ARL
$ARLP025
ARLP025
Propagation
Forecast
ZCZC AP25
QST de W1AW
Propagation
Forecast
Bulletin 25
ARLP025
From ARRL
Headquarters
Newington, CT
June 19, 2026
To all radio
amateurs
SB PROP ARL
ARLP025
ARLP025 The
ARRL Solar
Report
Solar activity
has been low
with only
C-class solar
flare
activity.
Region 4465
underwent some
decay and only
produced a
low-level
C-class flare.
Region 4469
decayed
further and
was inactive.
Region 4470
underwent some
growth, but
did not
increase in
magnetic
complexity and
was primarily
inactive.
The largest
solar flare of
the period, a
C2.5 on June
17, came from
just beyond
the west limb
with the
likely source
being recently
rotated
out-of-view
Region 4464.
A coronal mass
ejection (CME)
became visible
in STEREO
coronagraph
imagery on
June 17 and
Compact
Coronagraph
(CCOR) imagery
approximately
30 minutes
later. This
eruption was
first
determined to
be far-sided
due to SUVI
304 and 193
imagery;
however, the
backfilling of
a SOHO LASCO
data gap
prompted a
re-analysis
and it has
since
concluded that
there may be
an
Earth-directed
component.
Modeling is
currently
ongoing.
There was an
additional,
faster,
eruption off
the east limb
close to the
equator, with
the resulting
CME first
appearing in
LASCO C2
imagery on
June 17. Due
to its
faintness,
this CME is
not visible in
other
coronagraphs.
Modeling of
this event is
also ongoing,
but a
significant
Earth-directed
component is
not
anticipated.
Solar activity
is likely to
continue at
low levels
through June
20, with a
slight chance
for M-class
(R1-minor)
solar flares
due primarily
to the
combined flare
probabilities
of Regions
4465 and 4470.
Solar wind
parameters
were
indicative of
a weak
disturbance in
the
interplanetary
magnetic field
(IMF), which
was probably
related to
anticipated
early-stage
coronal hole
high speed
stream (CH
HSS)
influences.
The phi angle
was quite
variable
between
sectors.
Solar wind
speed
increased from
400 km/s to
nearly 500
km/s before
declining to
about 450
km/s. Mild
solar wind
disturbances
and
enhancements
are
anticipated
through June
20 due to weak
positive
polarity CH
HSS effects.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere
June 19 by F.
K. Janda
OK1HH:
The low solar
activity
observed
during the
second decade
of June will
be replaced by
significantly
higher
activity in
the third
decade, as the
active regions
observed by
the Solar
Orbiter on the
far side of
the Sun will
gradually
emerge.
Geomagnetic
activity will
generally be
relatively
low, and
shortwave
propagation
conditions
will be
relatively
favorableówithin
the limits of
the summer
ionosphere in
the Earthís
northern
hemisphere,
that is.
And, as was
the case in
the second
third of June,
we can expect
a significant
influence from
the sporadic E
layer.
The Predicted
Planetary A
Index for June
20 to June 26
is 10, 5, 8,
12, 5, 5, and
5 with a mean
of 7.1. The
Predicted
Planetary K
Index is 3, 2,
3, 4, 2, 2,
and 2 with a
mean of 2.6.
10.7
centimeter
flux is 132,
130, 112, 135,
136, 138, and
140 with a
mean of 131.9.
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
|
