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SB PROP @ ARL
$ARLP023
ARLP023
Propagation
Forecast
ZCZC AP23
QST de W1AW
Propagation
Forecast
Bulletin 23
ARLP023
From ARRL
Headquarters
Newington, CT
June 5, 2026
To all radio
amateurs
SB PROP ARL
ARLP023
ARLP023 The
ARRL Solar
Report
Solar activity
went from low
to high this
week.
Activity was
dominated by
Region 4455,
which produced
frequent
C-class flares
alongside
three
significant
flare events:
an M9.3/Sf on
June 1; as
well as an
M7.7/1b and an
X1.0/1n on
June 3.
There are
eight numbered
regions on the
visible disk.
Region 4455
remains
complex,
maintaining
its anti-Hale
configuration
and displaying
a newly
developed
delta
structure.
Continuous
flux emergence
and spot
growth with
penumbral
development
were observed
just ahead of
its mature,
positive
polarity lead
spot.
Regions 4458
and 4459 both
showed growth
and
consolidation,
with Region
4459 showing
rapid spot
development in
its trailing
area and
gaining a
mixed-polarity
gamma
configuration.
Region 4461
also showed
flux emergence
driving a
gamma
configuration,
though extreme
foreshortening
near the limb
limits
high-confidence
analysis of
its overall
complexity.
Region 4462
consolidated
and showed
increased
separation
between its
poles.
The remaining
regions were
stable or in
decline.
Several
eruptive
events
occurred
during the
reporting
period.
An M9.3/Sf
flare June 1
was
accompanied by
wideband radio
emissions,
including a
Type IV radio
sweep with an
estimated
shock velocity
of 253 km/s,
and a 10.7-cm
radio burst.
An associated
coronal mass
ejection (CME)
became visible
in LASCO C2
imagery on
June 2. While
faint in
coronagraph
imagery,
GOES/SUVI
imagery
implies a
partial to
full halo
profile, and
COR2
triangulation
confirms an
Earth-directed
component.
Modeling
indicates this
event is the
most
Earth-directed
CME of the
period s
events.
The M7.7/1B
flare on June
3 was
accompanied by
wideband radio
emissions,
including a
Type IV sweep,
a Type II
sweep with an
estimated
shock velocity
of 313 km/s,
and a
prominent
three-minute
10.7-cm radio
burst. The
associated CME
was first seen
in LASCO C2 on
June 3.
GOES/SUVI 304
imagery shows
much of the
ejecta was
deflected
significantly
northward by
an adjacent
positive
polarity
coronal hole.
STEREO COR2
imagery and
modeling shows
that, while it
retains an
Earth-directed
glancing
component, it
is the least
directly-targeted
event of the
period.
Solar activity
is expected to
be at moderate
to high levels
through June
6. M-class
(R1-R2/minor-moderate)
flaring
remains
likely, with a
slight chance
for X-class
(R3/strong or
greater)
events,
primarily due
to the
eruptive
capabilities
of Regions
4455, 4458,
and 4459.
Solar wind
parameters
continued to
be slightly
elevated with
conditions
reflecting
possible
embedded
transient
influences.
Wind speeds
held steady
near 400 km/s
for most of
the period
before a
distinct
increase to
near 450 km/s
late in the
period.
The phi angle
showed a
distinct
transition
into the
positive (away
from the Sun)
sector late in
the period.
Mild
enhancements
are expected
early on June
4 under the
initial onset
of positive
polarity
high-speed
stream (+CH
HSS)
influences.
Conditions
will escalate
dramatically
mid-to-late on
June 4 with
the arrival of
the multiple
June 3 CMEs.
These
significant
enhancements
are expected
to persist
through June 5
with elevated
conditions
persisting
through June
6.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere,
June 4, 2026,
by F. K.
Janda, OK1HH:
On May 28, a
large sunspot
group, AR
4455, began to
emerge on the
northeastern
limb of the
solar disk.
Its activity
had already
been monitored
in the
preceding days
by the Solar
Orbiter
spacecraft,
while we were
also aware of
it thanks to
helioseismological
observations.
In the first
days of June,
AR 4455
gradually
grew, while
its
configuration
pointed to
future growth
in eruptive
activity.
A series of
moderately
energetic
eruption
eruptions on
June
2 turned out
to be
precursors.
The main
event,
featuring four
energetically
significant
eruptions,
took place on
June 3, with
at least two
of them
accompanied by
a coronal mass
ejection
(CME), while
at least one
of which was
headed
directly
toward Earth.
These lines
you are
currently
reading are
being written
on June 4 at
around 16:00
UT, just
before more
than one
particle cloud
is expected to
hit Earth,
marking the
start of a
geomagnetic
disturbance.
The
disturbance is
expected to
intensify on
June 5 and is
likely to
continue,
albeit with
lower
intensity, on
June 6.
The latest
development in
solar activity
therefore
differs
significantly
from what we
witnessed in
May, during
the previous
solar
rotation, when
solar activity
was low and
the
magnetosphere
remained calm
in the
following
days.
Conclusion:
Ionospheric
propagation
conditions
during the
first weekend
of June will
be variable
and generally
poor, with low
MUF values.
Although a
noticeable
improvement is
expected in
the coming
days due to
increased
solar
activity,
another
geomagnetic
disturbance
can be
expected as
early as June
10. The only
certainty is
change!
The latest
solar report
from Dr.
Tamitha Skov,
WX6SWW, can be
found on
Youtube at https://www.youtube.com/watch?v=P0J2EQJWKIA
The Predicted
Planetary A
Index for June
6 to June 12
is 8, 5, 5, 5,
5, 30, and 25
with a mean of
11.9. The
Predicted
Planetary K
Index is 3, 2,
2, 2, 2, 6,
and 5 with a
mean of 3.1.
10.7
centimeter
flux is 125,
125, 120, 120,
130, 135, and
135 with a
mean of 127.1.
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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