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ARRL Propagation Bulletin ARLP012 (2011)

ARLP012 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 12  ARLP012
From Tad Cook, K7RA
Seattle, WA  March 25, 2011
To all radio amateurs 

ARLP012 Propagation de K7RA

All solar indicators were lower again for the second consecutive
week.  Average daily sunspot numbers declined over 28 points from
the week before to 40.9, and average daily solar flux was off over
18 points to 94.8.

But looking at solar images from the STEREO mission at we can see a great deal of activity
about to rotate toward us over the Sun's eastern horizon.  The whole
"back" side of our Sun looks very busy.

The March 24 NOAA forecast for solar flux and planetary A index sees
solar flux for March 25 to April 3 at 110, 115, 120, 125, 125, 130,
130, 130, 120 and 115.  Planetary A index for the same period is
predicted at 5 for March 25-29, 7 on March 30-31, and 5 on April

This indicates improving HF propagation for the near term, with
geomagnetic indicators unsettled only very slightly compared to
recent very quiet conditions.  Conditions should be good for the CQ
World Wide WPX SSB Contest this weekend, and there is a useful web
site devoted to this contest at

Geophysical Institute Prague has a forecast for geomagnetic
conditions quite different from NOAA, predicting quiet conditions
for March 25-27, unsettled to active on March 28, unsettled March
29-30, and quiet to unsettled March 31.

Carl Luetzelschwab, K9LA pointed out that the nanoTesla values for
each level of K index mentioned in last week's bulletin are actually
for the Boulder, Colorado magnetometer, and the values are different
for each observatory.  He has a good description of how this all
works at his web site,

Jeff Hartley, N8II of Shepherdstown, West Virginia sent in a report
last Saturday, March 19.  He wrote, "Despite the decline in solar
activity 12 meters has been consistently open to Europe every
weekday this week including some Russians, Latvia, and Lithuania. As
the flux has dropped off, the band has been opening later. The band
was wide open to Europe at 1230Z Monday (March 14), Thursday and
Friday (March 17-18) were good from about 1445Z to past 1600Z. 15
meters has been consistently good to Russia with loud signals (RL3A
S9+20-30dB) and even central Asia including UK6, UK8, and UN3M (S9)
worked 2 days and I even caught HS0ZDS on Wednesday right over the
pole. The low K indexes seem more important than the high flux for
anything close to the pole, no big surprise. VU4PB had a good signal
Thursday (March 17) on 17 meters from 1300-1500Z and quite a few USA
stations, including me, were getting thru the European pile for a
new one."

NASA has a video at
explaining the very low sunspot activity over the past few years.

MIT Technology Review at has an article
about the double-peak of many sunspot cycles.

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 Find more good
information and tutorials on propagation 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 17 through 23 were 45, 35, 48, 47, 34, 31,
and 46, with a mean of 40.9. 10.7 cm flux was 90.1, 87.6, 88.8, 92,
101, 99.8, and 104.6, with a mean of 94.8. Estimated planetary A
indices were 3, 2, 4, 4, 4, 6, and 10, with a mean of 4.7. Estimated
mid-latitude A indices were 2, 2, 2, 4, 4, 5, and 9, with a mean of


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