ARRL Propagation Bulletin ARLP007 (2011)

ARLP007 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 7  ARLP007
From Tad Cook, K7RA
Seattle, WA  February 18, 2011
To all radio amateurs 

ARLP007 Propagation de K7RA

A dramatic surge in solar activity is underway, with a level of
sunspot numbers and solar flux not seen since 2005-2006.  Tuesday's
sunspot number of 100 has not been equaled or exceeded since April
6, 2006 when it was 105.  On Wednesday the solar flux was 114.1, and
the last time it was that high or higher was September 15, 2005 at

Average daily sunspot numbers rose this week by more than 25 points
to 69.9, and average daily solar flux was up 20 points to 103.5.

NOAA/USAF predicts solar flux at 110 on February 18-19, 105 on
February 20, 100 on February 21, and 105 on February 22-24.
Planetary A index is predicted at 25 and 12 on February 18-19, and 5
on February 20-28, then rising to 7, 10, 10 and 7 on March 1-4.

Geophysical Institute Prague predicts active conditions on February
18, unsettled to active February 19, unsettled February 20, quiet to
unsettled February 21, and quiet conditions February 22-24.

This weekend is the ARRL International DX CW Contest, and Bob
Marston, K6TW notes that a geomagnetic storm is predicted for
Friday, just before the start of the contest.  This is due to two
coronal mass ejections, one on February 13 at 1735z, and the other
on February 15 at 0156z.  A CME hit Earth's magnetic field at 0100z
today, February 18, but was not as strong as expected.  It is
possible we may be spared major geo-storms.  However, there is a new
alert from Solar Storm Watch of an expected CME direct hit at 0900z
on February 18.  The planetary K index on February 18 at 0300, 0600
and 0900z was 3, 4 and 5.

Most of the activity this week has been from large sunspot group
1158, which will soon rotate out of view over the Sun's western
limb.  More centrally positioned is sunspot 1161, and there seems to
be a new sunspot emerging above it.  It is probably significant that
USAF/NOAA revised the solar flux estimate upward for the near term
between Wednesday's and Thursday's prediction.

K6TW introduced us to a resource for updates on solar activity,, and specifically a Twitter resource,
which you can read without a Twitter account at

Fred Honnold, KH7Y of Ocean View, Hawaii (south part of the big
island of Hawaii) has a report of some 10 meter longpath to Europe
propagation on February 14.

"I wanted to let you know about some excellent long path QSO last
night from 0923 till 1055.  The bands were still alive but it was
1AM here and I just quit.  Signal levels on 15 meters from the KW
stations were S8 or so on 12 meters the signals were still strong so
after working about 100 stations on 12 meters I moved to 10 meters.
I worked many European stations with signals S1 to S5.  The best
signals were from EA1DR S9+ and S57S very loud."

You can see the spots by going to DX Sherlock at  Just select 28 MHz, February 14 from
1000z to 1059z, containing the callsign KH7Y, set maximum number of
returned QSOs at 100, then Submit Query.

An article on the ARRL web site about sunspot 1158 and this week's
activity mentions that "According to NASA, the Sun will reach its
next maximum this year, give or take one year."

I don't think this is true, as the latest prediction for the next
solar maximum is in 2013.  If you check a recent Preliminary Report
and Forecast at,
look on page 10 and note that the highest smoothed sunspot number in
the near future is 90, predicted for February through July 2013.

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

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bulletins are at

Sunspot numbers for February 10 through 16 were 38, 54, 63, 84, 90,
100, and 60, with a mean of 69.9. 10.7 cm flux was 91.4, 91.2, 95.6,
106.8, 112.6, 112.8 and 114.1 with a mean of 103.5. Estimated
planetary A indices were 3, 4, 4, 2, 10, 5 and 2 with a mean of 4.3.
Estimated mid-latitude A indices were 4, 3, 2, 1, 6, 4 and 1 with a
mean of 3.