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ARRL Propagation Bulletin ARLP044 (2011)

ARLP044 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 44  ARLP044
From Tad Cook, K7RA
Seattle, WA  November 4, 2011
To all radio amateurs 

ARLP044 Propagation de K7RA

First, a few solar cycle updates. As you might suspect, the average
daily sunspot numbers for October shot way up, from 55.5 in June, to
67.2 in July, 66 in August, 106.4 in September, and 123.6 in

Our three month moving average of daily sunspot numbers was also up,
of course, with the three month average ending in October at 98.6,
up from 61.5 in July, 63 at the end of August, and 70.6 ending in

Because of increasing solar activity, for the third consecutive
month NASA revised its prediction for the peak of the current solar
cycle, each time estimating higher intensity and changing the
projection for the month the cycle is expected to peak.

Note that these numbers are not the higher Boulder sunspot numbers
we report here, but the much lower Zurich numbers. They are also
smoothed sunspot numbers, meaning they represent an average taken
over a year, with the indicated month in the middle.

September 1 they moved the expected peak from June 2013 to May 2013,
and the smoothed sunspot number from 69 to 70. At one time they were
predicting a maximum nearly the same as the 1907 maximum of Cycle
19, 64.2, but of course recent predictions are substantially above
that value. NASA noted that the current cycle would still be the
smallest in the past hundred years.

A month later on October 3 they upped it again, with the maximum
smoothed sunspot number jumping from 70 to 77, and the peak moving
again, this time from May to April 2013. But at this level, it would
still be the weakest cycle in 100 years.

This time on November 2 their prediction made a big jump, from 77 to
89, but with the peak moving back out, this time from April to May
2013. This makes the cycle slightly bigger and longer, and instead
of 100 years, it is the smallest solar cycle in over 80 years.

Their prediction for solar max jumped nearly 30% in three months -
not bad. Still, a graphic comparing the beginning of this cycle with
the last three shows how weak it really is.  See But note this is a 13
month moving average, so the latest point on the graph is over 6
months ago, and the higher activity is recent.

The latest prediction from NOAA and USAF for the near term has solar
flux at 165 on November 4-10, 160 on November 11, and 150 on
November 12-15, 160 on November 16, and peaking again at 165 on
November 17-18, then falling to 155, 145, 140 and 130 on November

For November 4-6 the predicted planetary A index is 15, 10, and 8,
then 5 on November 7-10, 12, 10, 8, and 5 on November 8-10, 8 on
November 11-13, and 5 again on November 14-23.

Geophysical Institute Prague predicts quiet to unsettled conditions
November 4, unsettled November 5, quiet to unsettled November 6, and
quiet conditions November 7-10.

A huge sunspot group, number 1339, with an area of 1400 millionths
of a solar hemisphere has rotated into view. There was one new
sunspot group on October 30, three more on October 31, another two
on November 1, and another new one on November 2. On Thursday,
November 3, sunspot group 1339 was reported to be the biggest
sunspot in a number of years. The total sunspot area for that day
was 2005 millions of a solar hemisphere, and a larger total sunspot
area has not been observed since July 18-23, 2004, when total
sunspot areas were 2300, 2325, 2190, 2420, 2070, and 2050. It is
interesting that no new sunspots appeared during that period, and
the daily sunspot numbers were 169, 176, 147, 162, 117 and 86 over
those same six days.

The Sun is currently peppered with spots, so don't be surprised if a
solar flare is released, possibly disrupting HF radio communications
if it is aimed at earth.  MSNBC ran an article on the latest solar
activity, which you can read at,

You can also watch a video of a flare from sunspot group 1339 at,

Note that you can select twice the default resolution by clicking on
the 360p at the bottom, and restarting the video. This gives a very
good picture for full screen viewing, accessed by clicking in the
lower right of the screen.

Scott Smith, VK2AET of New South Wales, Australia wrote to say, "I
was enjoying a CW contact with the USA on 10 meters today (November
3) at 2015 UTC when all of a sudden the band went completely dead.
Before this I had just worked EA8 which was quite exciting. After
this fadeout there were no signals at all on 10 meters. It appeared
so dead that I thought my antenna had fallen down and I had to look
out the window at it. Here in VK we get a great indicator of 10
meter propagation by listening to 27.025 MHz where US CBers are
usually well over S9 when the band is in good shape.  These guys had
also disappeared completely whereas half an hour before they were
their usual strength."

Scott must have observed an effect from the X-Class solar flare,
which peaked about 12 minutes later at 2027 UTC. That is the same
flare reported in the article at Universe Today linked above.

ARRL CW Sweepstakes is this weekend, and the current solar activity
should make 10 meters especially productive. See

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 October 27 through November 2 were 98, 104, 73,
80, 112, 141, and 121, with a mean of 104.1. 10.7 cm flux was 131.5,
133.9, 123, 126.7, 138.1, 138.6, and 153.6, with a mean of 135.1.
Estimated planetary A indices were 4, 2, 2, 6, 8, 21, and 11, with a
mean of 7.7. Estimated mid-latitude A indices were 4, 1, 2, 4, 9,
14, and 7 with a mean of 5.9.


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