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ARRL Propagation Bulletin ARLP043 (2015)

ARLP043 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 43  ARLP043
From Tad Cook, K7RA
Seattle, WA  October 23, 2015
To all radio amateurs 

ARLP043 Propagation de K7RA

Average daily sunspot numbers over the past week were up 38.1 points
to 75, and average daily solar flux rose 30.7 points to 118.2.
Geomagnetic conditions were quiet over the week, with average
planetary A index declining from 25.1 to 11, and mid-latitude A
index dropping from 17.6 to 9.1.

Predicted solar flux is 125 on October 23-25, 120 on October 26-28,
115 on October 29-30, 85 on October 31 through November 1, 80 on
November 2-6, then 85, 90, 95, 100, 105, 110, 115 and 120 on
November 7-14, 125 on November 15-17, 120 on November 18-20, and 115
on November 21-22. Flux values then drop to 80 on November 28
through December 3.

Predicted planetary A index is 5, 12, 24 and 8 on October 23-26,
then 5, 8, 12 and 10 on October 27-30, 5 on October 31 through
November 2, 50 on November 3, 40 on November 4, 25 on November 5, 12
on November 6-7, then 20, 25, 20 and 10 on November 8-11, and 8 on
November 12-13. A index then drops to 5 on November 19-24, then
bounces back to 50 on November 30.

Those Ap index values of 50 on November 3 and again on November 30
seem to be echoes of the October 7-8 period when planetary A index
was 77 and 56. The high values are each spaced one whole solar
rotation (27-28 days) from each other.

F.K. Janda, OK1HH sent us his weekly prediction for geomagnetic
conditions. He believes the geomagnetic field will be mostly quiet
October 23, quiet to active October 24, quiet to unsettled October
25, quiet on October 26, mostly quiet October 27, quiet to active
October 28, mostly quiet October 29, quiet to active October 30
through November 1, active to disturbed November 2, quiet to active
November 3, active to disturbed November 4, mostly quiet November
5-6, quiet to unsettled November 7, quiet to active November 8,
active to disturbed November 9, quiet to active November 10, mostly
quiet November 11-12, quiet to unsettled November 13-14, mostly
quiet November 15, quiet to unsettled November 16, and quiet to
active November 17.

OK1HH expects increased solar wind on October 29-31, November 2-5,
10-11, 15, 18 and 19-20. The days October 29-30, November 2, 5,
10-11 and 19-20 have a lower probability of increased solar wind.

Now what do all these numbers mean? For good HF conditions we like
to see a quiet geomagnetic field, and higher solar flux and sunspot
numbers. The A index also represents geomagnetic conditions, and for
this, single-digit numbers are desirable, the lower the better. An A
index about 10 represents unsettled to active conditions and when it
gets toward 50, this is a geomagnetic storm.

The main reason we like low geomagnetic numbers is the higher
numbers may indicate higher absorption.

for a good explanation of A index and other solar indices.

Dave Ballard, W2VK and David Moore both sent in a Science Daily
article about some large solar storms perhaps being undetected. Read
it at .

Ray Price, KE4YOG of Goldsboro, North Carolina wrote: "12 meters has
been fun lately. I worked 9K2WA (Kuwait) on 21 October at 1518 UTC
along with several other stations. On 22 October at 2145 UTC I
worked V73D (Marshall Islands) for a ATNO (All Time New One) on
24.955 MHz. I haven't been able to be on but an hour or two here and
there, but 12 meters has been fun.

"All were worked with a Kenwood TS480HX running 200 watts into a 230
Doble up about 60 feet in the sycamore trees."

The reference to the "230 Doble" had me scratching my head, but I
think he may be referring to a 230 foot long doublet. If so, that's
a dipole about 6 wavelengths long on 12 meters.

Don't forget, this weekend is the SSB portion of the CQ Worldwide DX
Contest.  See . Conditions should be
good, with no predicted geomagnetic storm until November 3.

If you would like to make a comment or have a tip for our readers,
email the author at,

For more information concerning radio propagation, see the ARRL
Technical Information Service web page 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
the download.

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 October 15 through 21 were 49, 68, 83, 81, 94,
77, and 73, with a mean of 75. 10.7 cm flux was 106.8, 109.1, 116.6,
119.5, 123.7, 122.8, and 129, with a mean of 118.2. Estimated
planetary A indices were 10, 8, 11, 22, 5, 9, and 12, with a mean of
11. Estimated mid-latitude A indices were 9, 8, 9, 15, 3, 8, and 12,
with a mean of 9.1.


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