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ARRL Propagation Bulletin ARLP034 (2015)

ARLP034 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 34  ARLP034
From Tad Cook, K7RA
Seattle, WA  August 21, 2015
To all radio amateurs 

ARLP034 Propagation de K7RA

Solar activity declined over the past reporting week, August 13 to
19.  Average daily sunspot numbers went from 82.3 during the
previous seven days, to 37.4 in the most recent period.
Average daily solar flux also declined over the same two weeks, from
a mean of 112.4 to 91.  Average planetary A index went from 11.7 in
the previous week to 21.4 in the recent seven days.  Activity over
August 15 to 17 drove these numbers higher, with planetary A index
at 44, 36 and 27 during those three days.  This was caused by a CME,
a coronal mass ejection.
The latest predicted solar flux from NOAA/USAF over the near term is
105 and 110 on August 21 and 22, 115 on August 23 and 24 then 110,
115, 110 and 100 on August 25 to 28, 95 on August 29 through
September 2, 100 on September 3 and 4, 105 on September 5, 100 on
September 6 and 7, then 95 and 90 on September 8 and 9, and 85 on
September 10 to 18.  Solar flux then rises to 100 after September
Predicted planetary A index is 12 on August 21 and 22, 28 on August
23, then 12, 8, 12 and 14 on August 24 to 27, 10 on August 28 and
29, 5 on August 30 through September 1, then 12, 22, 15 and 12 on
September 2 to 5, 10 on September 6 and 7, then 8 on September 8 and
9, 5 on September 10 and 11, then 10, 20 and 15 on September 12 to
14, 5 on September 15 and 16 and 8 on September 17 and 18.
OK1MGW sent a geomagnetic forecast for August 21 to September 16. He
sees quiet to unsettled conditions August 21 and 22, quiet to active
August 23, quiet to unsettled August 24, mostly quiet August 25, and
active to disturbed August 26 (although he is unsure of the
reliability of that prediction).
On August 27 and 28 he sees quiet to active conditions, quiet to
unsettled August 29 and 30, mostly quiet August 31 through September
1, quiet to active September 2, active to disturbed September 3,
quiet to active September 4, mostly quiet September 5 to 8, quiet
September 9 and 10, mostly quiet September 11, quiet to unsettled
September 12 to 15 and quiet to active September 16.  He expects
increases in solar wind August 23, 25 to 28 and September 1 to 4.
At 0636 UTC on August 19 Australia's Space Weather Services released
a geomagnetic disturbance warning, which said, "A large Coronal Hole
(CH 683) is located in the solar Northern Hemisphere and is taking
geoeffective position.  A high speed solar wind stream emanating
from CH 683 is driving a Co-rotating Interaction Region (CIR) and
this will affect Earth's geomagnetic environment over the next 1 to
2 days.  Minor geomagnetic storms could occur in the high latitude
regions and possibly extend into the mid latitudes.  The aurora may
be visible from the southern parts of Australia at the local night
hours on 19 and 20 August."
Jon Jones, N0JK of Kansas wrote: "A surprising amount of late season
sporadic E propagation on 50 MHz this third week of August.
Six meters was open for strong sporadic E the afternoon and evening
of August 16.  In addition to strong single hop, some double hop
E-skip was noted by W9RM DM58 to FM18, and K1TOL FN44 to N3AIU in
DM45 around 0200z August 17.
The next day and afternoon sporadic E appeared again.  This time
multi-hop Es spanned the Atlantic Ocean between North America and
CT1HZE IM57 worked into W5, W9 and W0 around 1600z, then again to
the Midwest starting at 2245z on 6 meters.  N0LL EM09 and KQ0J EN11
worked CT1HZE around 2315z.  KQ0J was using just a single loop
antenna.  I did not hear CT1HZE in eastern Kansas, but picked up
W7LFB on 50.160 MHz in very rare DN83.  Finally N0LL also worked a
rare grid, VE9IQ FN67 for Larry's last grid to complete the FFMA
(Fred Fish Memorial Award) at 2327z.
The geomagnetic field had been active all weekend due to a CME
impact August 15, which caused a strong G3-class geomagnetic storm
and bright auroras around the Arctic Circle.  The storm persisted as
a G1-class through August 17, perhaps enhancing sporadic E
For more information concerning radio propagation, see the ARRL
Technical Information Service at  For an explanation of
the numbers used in this bulletin, see  An archive of
past propagation bulletins is at  More good
information and tutorials on propagation are at
My own archives of the NOAA/USAF daily 45 day forecast for solar
flux and planetary A index are in downloadable spreadsheet format at and .
Click on "Download this file" to download the archive and ignore the
security warning about file format.  Pop-up blockers may suppress
download. I've had better luck with Firefox than IE.
Monthly propagation charts between four USA regions and twelve
overseas locations are at
Instructions for starting or ending email distribution of ARRL
bulletins are at
Sunspot numbers for August 13 through 19 were 51, 46, 33, 32, 20,
44, and 36, with a mean of 37.4. 10.7 cm flux was 94.8, 93.2, 89.4,
85.6, 87, 88.7, and 98.2, with a mean of 91.  Estimated planetary A
indices were 11, 4, 44, 36, 27, 9, and 19, with a mean of 21.4.
Estimated mid- latitude A indices were 14, 4, 24, 27, 27, 10, and
18, with a mean of 17.7.


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