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Subject: ARLP021 Propagation Forecast
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From: "ARRL"
Date: Sat, 23 May 2026 09:26:00 EDT
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>SB PROP @ ARL $ARLP021
>ARLP021 Propagation Forecast
ZCZC AP21
QST de W1AW
Propagation Forecast Bulletin 21 ARLP021
>From ARRL Headquarters
Newington, CT May 22, 2026
To all radio amateurs
>SB PROP ARL ARLP021
>ARLP021 The ARRL Solar Report
Solar activity continued at low levels during the past 24 hours with four
active regions on the visible disk.
The largest events were a C1.0 on May 20 from the northeast limb and a
C1.0/Sf, also on May 20, from Region 4439 that was accompanied by Type-III
radio sweeps. This region was responsible for the majority of the periods
activity, which otherwise included a B8.7 flare on May 20 from Region 4436.
Region 4441 showed some development during the period while 4443 remained
stable. Coronal activity was observed in CCOR-1 imagery after May 20, but
additional data is needed for further analysis.
Solar wind parameters trended toward background conditions with speeds
reaching a peak of 542 km/s on May 20 and then decreasing steadily throughout
the reporting period, ending at ~450 km/s.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere
May 22 - May 28, 2026 by F. K. Janda, OK1HH
The number of sunspot groups on the solar disk ranged from three to seven
over the past week; their total area was not large, while their magnetic
structure was relatively simple.
Nevertheless, isolated C-class flares were recorded.
In addition, there was even an M-class flare recorded on Sunday, May 17 (in
AR 4435 near the northwestern limb of the solar disk, peaking at 0339 UT).
Thanks to the Solar Orbiter probe, however, we know that the situation will
change.
Because, in a location where there was no group of sunspots during the
previous solar cycle, not only is there a group now, but it is also quite
extensive.
Its edge is already slowly beginning to appear on the southeastern limb of
the solar disk.
While a week later, we can expect the peak of activity within the current
solar rotation.
The geomagnetic field will be mostly quiet to unsettled in the coming days,
after which its activity will rise, initially slightly, and a disturbance can
be expected toward the end of the month. This will result in a generally
favorable development for the ionosphere for the remainder of May. This
includes increases in geomagnetic activity, during which, depending on the
timing, MUF values may temporarily rise.
The Predicted Planetary A Index for May 23 to May 29 is 5, 5, 5, 5, 12, 10,
and 8 with a mean of 7.The Predicted Planetary A Index for May 23 to May 29
is 5, 5, 5, 5, 12, 10, and 8 with a mean of 7.1. The Predicted Planetary K
Index is 2, 2, 2, 2, 4, 3, and 3 with a mean of 2.6. 10.7 centimeter flux is
112, 112, 115, 115, 115, 120, and 125 with a mean of 116.3.
For more information concerning shortwave radio propagation, see
www.arrl.org/propagation [
http://www.arrl.org/propagation?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] and the ARRL Technical Information Service webpage at
www.arrl.org/propagation-of-rf-signals [
http://www.arrl.org/propagation-of-rf-signals?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] . For an explanation of numbers used in this bulletin, see
www.arrl.org/the-sun-the-earth-the-ionosphere [
http://www.arrl.org/the-sun-the-earth-the-ionosphere?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] . Information and tutorials on propagation can be found at http://k9la.us [
http://k9la.us ] .
Also, check this: "Understanding Solar Indices" from September 2002 QST.
https://bit.ly/3Rc8Njt [ https://bit.ly/3Rc8Njt ]
ARRL The National Association for Amateur Radio(R)
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