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SB PROP @ ARL
$ARLP024
ARLP024
Propagation
Forecast
ZCZC AP24
QST de W1AW
Propagation
Forecast
Bulletin 24
ARLP024
From ARRL
Headquarters
Newington, CT
June 12, 2026
To all radio
amateurs
SB PROP ARL
ARLP024
ARLP024 The
ARRL Solar
Report
Solar activity
has been at
low levels
this past
week, with
most of the
C-level
activity
originating
from Region
4465,
including the
largest flare
of the week, a
C2.6 observed
on June 10.
There are
currently 7
numbered
sunspot
regions on the
disk, with
Region 4467
decaying to
plage.
There was a
Type-II radio
sweep detected
by the Radio
Solar
Telescope
Network (RSTN)
on June 10.
That radio
emission was
associated
with a coronal
mass ejection
(CME) first
observed at
the NE
quadrant by
ground-based
coronagraph
imagery from
HAO/MLSO
coronagraph
late June 10,
and later by
space-based
coronagraph
LASCO/C2.
Modeling
indicates
there is no
Earth-directed
component.
Other CME
activity was
observed in
the
coronagraph
imagery later
in the period,
but
preliminary
analysis
indicated no
Earth-directed
component.
Solar activity
is expected to
remain at low
levels, with a
chance for
M-class flares
and a slight
chance for
X-class
flares.
NOAAís SOLAR-1
satellite
became
operational
early on June
11, becoming
the Space
Weather
Prediction
Centerís
primary source
of solar wind
data.
Solar wind
speeds
continued to
decrease after
the passage of
a weak
transient,
reaching 374
km/s at the
end of the
period.
Background
solar wind
conditions are
expected
through midday
June 11, when
a coronal hole
high-speed
stream (CH
HSS) is
anticipated to
become
geoeffective
through June
13.
Weekly
Commentary on
the Sun, the
Magnetosphere,
and the
Earth's
Ionosphere,
June 11, 2026,
by F. K.
Janda, OK1HH:
Overall solar
activity is
rather low and
is expected to
continue and
decline
through
mid-June. Most
active regions
are relatively
small,
typically with
a simple
magnetic
configuration.
Nevertheless,
class C flares
are
occasionally
observed,
sometimes
accompanied by
CMEs.
Currently,
CMEs from June
9 and 11 are
expected to
arrive,
leading to an
increase in
geomagnetic
activity from
June 12 to 14.
A period of
several days
of calm
activity is
predicted to
begin on June
16.
Shortwave
propagation
has begun to
be
significantly
affected by
the sporadic E
layer, while
its increased
activity can
be expected to
continue over
the next few
days.
The Predicted
Planetary A
Index for June
13 to June 19
is 6, 6, 8, 8,
5, 5, and 5
with a mean of
6.1. The
Predicted
Planetary K
Index is 2, 2,
3, 3, 2, 2,
and 2 with a
mean of 2.3.
10.7
centimeter
flux is 128,
120, 118, 120,
122, 122, and
125 with a
mean of 122.1.
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.
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