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ARRL Propagation Bulletin ARLP013 (2015)

ARLP013 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 13  ARLP013
From Tad Cook, K7RA
Seattle, WA  March 27, 2015
To all radio amateurs 

ARLP013 Propagation de K7RA

Sunspot numbers and solar flux both rose this week. Average daily
sunspot numbers from March 19 to 25 were up 24.8 points to 83.9,
compared to the previous seven day period. Average daily solar flux
rose from 117.5 to 122.4.
Average planetary A index dropped from 29.4 to 19.4, although
conditions continued to be active. March 22 and 23 had planetary A
index numbers at 24 and 21, but there was nothing like the number
117 on March 17, a huge, huge level for the A index.
We saw one new sunspot region on March 19, two on March 21, three on
March 22 and three more on March 23, another new one on March 24 and
yet another two days later on Thursday, March 26.
Predicted solar flux is 135 on March 27 to 30, 145 on March 31 and
April 1, 140 on April 2 and 3, 130 on April 4 and 5, 125 on April 6
to 8, 120 on April 9 and 10, 115 on April 11 to 19, 120 on April 20,
115 on April 21, 120 on April 22 and 23, and 125 on April 24 to 27.
The forecast for the next few days changed dramatically from
Wednesday night's flux prediction, which had flux values at 150 on
March 27 and 28, 145 on March 29 and 30 and ran in the ARRL Letter.
As of Thursday night (March 26) the predicted value for all four of
those days sank to 135.
On March 25 the predicted planetary A index for March 26 was 8,
which turned out to be precisely correct. The latest A index
prediction shows 15 on March 27, 25 on March 28 and 29, then 15, 10
and 5 on March 30 through April 1, 12 on April 2 to 4, 5 on April 5
and 6, 8 on April 7 and 8, 5 on April 9 to 11, then 15 and 30 on
April 12 and 13, 20 on April 14 to 16, 15 on April 17, 20 on April
18 and 19, then 12, 5 and 15 on April 20 to 22, and 25 on April 23
and 24.
Petr Kolman, OK1MGW of the Czech Propagation Interest Group,
predicts geomagnetic conditions should be quiet to unsettled March
27, active to disturbed March 28 and 29, quiet to unsettled March 30
through April 2, quiet to active April 3, quiet to unsettled April 4
and 5, quiet on April 6, mostly quiet April 7 to 10, quiet to
unsettled April 11 and 12, active to disturbed April 13 to 16, quiet
to unsettled April 17, quiet to active April 18 and 19, and mostly
quiet April 20 to 22.  You can see that the geomagnetic conditions
are all over the place, with many active periods. This is typical
after the solar cycle passes its peak, which for cycle 24 was about
a year ago. You can see the peaks in the smoothed (averaged over a
whole year) sunspot numbers and solar flux in tabular form on pages
14 and 15 at 
It looks like sunspot numbers peaked around March through May 2014
and solar flux around May through July of the same year.
The word "Legacy" in the above URL reminds us that these weekly
publications are moving to
where you select the year of interest (in this case 2015, of course)
in the folder names toward the bottom of the page, then the
WeeklyPDF folder. 2015 began with prf2053.
John Burgoon, KC9TUI of Bloomington, Indiana wrote about his trip to
Florida, which coincided with the huge geomagnetic upsets of over a
week ago.
On March 23, John wrote, "Last week I went on vacation to Amelia
Island, Florida, happily toting my new 17 meter mobile home brew
system.  I had a carefully tuned dipole and a single vertical whip.
By the time we drove down, settled in, and finally got to the point
that I could set up on the beach, I could not hear much at all. On
Monday morning I heard a few signals, but no contacts. On Tuesday
March 17th all I heard was the background hiss of my radio. I set up
again on Thursday afternoon (19th) and again did not hear anyone.
Not a single contact. That's the breaks sometimes.
Next time I'll have more equipment, as I am currently building
radios for 40 meters, 20 meters, and 10 meters."
Check out John's bio on, and see what he is doing lately
with his homebrew projects.
Don't forget, the CQ World Wide WPX SSB Contest is this weekend,
March 28 and 29, and the CW weekend is the last weekend in April.
The cool thing about this contest is that every prefix worked is a
multiplier. So if your call begins with KQ4, that is a separate
multiplier from a call starting with WS1. You may have a rare
prefix, or even a unique one in the contest, making you sought after
like DX even though you are right here at home in the United States.
See for details.
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
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 March 19 through 25 were 71, 27, 40, 88, 119,
127, and 115, with a mean of 83.9. 10.7 cm flux was 109.3, 112.7,
113.6, 122.4, 128.1, 133, and 137.8, with a mean of 122.4. Estimated
planetary A indices were 28, 24, 14, 24, 21, 12, and 13, with a mean
of 19.4.  Estimated mid-latitude A indices were 19, 18, 12, 16, 16,
9, and 10, with a mean of 14.3.


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