ARRL

ARRL Propagation Bulletin ARLP006 (2012)

SB PROP @ ARL $ARLP006
ARLP006 Propagation de K7RA

ZCZC AP06
QST de W1AW  
Propagation Forecast Bulletin 6  ARLP006
From Tad Cook, K7RA
Seattle, WA  February 10, 2012
To all radio amateurs 

SB PROP ARL ARLP006
ARLP006 Propagation de K7RA

Solar activity was down again this week. In fact this is the third
consecutive week in which sunspot numbers were lower than the prior
week. In Propagation Forecast Bulletin ARLP003 we reported an
average daily sunspot number of 116.9 for January 12-18, 98.7 the
next week, followed by 62 last week and now 40.4 during the latest
period.  The solar flux forecast - which roughly tracks sunspot
numbers; we don't have access to any short term sunspot number
forecast - has also been lowered steadily over recent weeks.

On Tuesday, February 7 the daily sunspot number was 24, the lowest
since mid-August 2011, when it was 0 and 13 on August 14-15.

Looking at the lower frame on the Solar Data Plotting Utility from
WA4TTK (see http://www.craigcentral.com/sol.asp for a copy), it
appears that we are down from a peak of activity late last year.
You can see the same trend at http://wm7d.net/hamradio/solar/ toward
the middle of the page, on the graph showing sunspot and flux values
over the past year.

In mid-January the solar flux forecast for February 17-21 was 165,
which was important because the ARRL International CW DX Contest is
on February 18-19. More sunspots and higher solar flux would mean
higher usable frequencies, increasing the chance that 10 and 15
meters would give good results.

By January 24 the prediction was down to flux values of 155 on
February 11-13, 150 on February 14-19 and 145 on February 20-23.

Then on February 4 the forecast went down again, with predicted flux
at 125, 130 and 155 on February 11-13, 150 on February 14-19, and
145 on February 20-23. The next day the forecast said 125 on
February 11, 130 on February 12-13, with the rest of the forecast
unchanged from a day earlier. Two days later on February 7 was
another downward revision, with flux of 100, 105, 110 and 115 on
February 11-14, and 110 on February 15-24.

A day later on February 8 it changed again, with solar flux at 100
on February 9-11, 105 on February 12, and 110 on February 13-24.
The latest forecast (February 9) is revised upward, with solar flux
of 105 and 115 on February 10-11,120 on February 12-13, 125 on
February 14, 130 on February 15-16, 120 on February 17 and 110 on
February 18-24.

Predicted planetary A index is 8 on February 10, 5 on February 11, 8
on February 12-13, 5 on February 14-22, 8 on February 23, and 5 on
February 24 through March 1.

Jon Jones, N0JK of Wichita, Kansas reports a couple of 6 meter
spots. On February 8 he heard XE2O/b (EL05) for over 2 hours, from
2330 UTC to after 0130 UTC on 50.068 MHz on E-skip. He also had
E-skip to Texas and Arizona.

Stations in the Dallas/Fort Worth area (W5LUA, WD5K, WU0R, etc)
worked FK8CP (New Caledonia, in the South Pacific) on 6 meters
around 0200 UTC February 9 via a trans-equatorial E-skip link.

Last week Jon reported hearing the C6AFP beacon (Bahamas) on 50.04
MHz on January 30 around 1700 UTC.

Russ Mickiewicz, N7QR of Portland, Oregon sent a link to an article
in IEEE Spectrum about risks to power grids from solar storms. Read
it at http://spectrum.ieee.org/energy/.  Look for the
the-smarter-grid/a-perfect-storm-of-planetary-proportions/0 link.

Randy Crews, W7TJ of Spokane, Washington has an observation about
recent solar conditions: "This bottom is the longest I can remember
since I was licensed in 1964. Usually we have about 12 months of
very low activity and the solar flux punches up over 100 in about
12-15 months from the cycle bottom. This time it took two-and-a-half
years, from the August 2008 low until February 14 2011. This time
last year the solar flux had not yet crossed 100. February 14 was
the real breakout, as chartists would say. Past solar cycles have
bottomed with a sunspot number of about 10-12. The sunspot number at
the bottom of the past cycle was approximately 1.5!  It's been a
long, long dry spell for the higher bands. Looking forward to the
150 values!"

Randy also notes, "Of all the winter months, February conditions are
unique. February is a combination for winter and spring propagation,
with increases in daylight of 3 minutes per day (at 49 degrees N.
Latitude) and still having very low D Layer absorption. Daylight is
approximately 10 hours in duration, and the grayline paths are
almost a carbon copy of those in October. Propagation will change
almost daily as spring approaches. It is an excellent time of the
year to DX or Contest."

Don't miss the excellent and thought provoking article about
propagation in the March 2012 issue of QST, "Three Wrong Assumptions
About the Ionosphere," by Eric Nichols, KL7AJ. Eric reminds us that
the ionosphere is not spherical or smooth, and he explains how
propagation through it is not reciprocal, or the same coming back as
it is going out.

And finally, the headline on the AP wire article read "Plane Crash
Held Caused by Sun Spots. Ghost Wave Blamed for Disaster." But the
date was December 1938, the peak of sunspot Cycle 17. Read it at
http://news.google.com/newspapers?id=2TVPAAAAIBAJsjid=U00DAAAAIBAJpg=6339,4097417dq=sunspothl=en.

If you look at the 20th century solar data at
http://wm7d.net/hamradio/solar/historical.shtml, you can spot the
peak of Cycle 17, two before the big one, Cycle 19, in the late
1950s.

If you would like to make a comment or have a tip for our readers,
email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at
http://arrl.org/propagation-of-rf-signals. For an explanation of the
numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past
propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. Find more good
information and tutorials on propagation at
http://myplace.frontier.com/~k9la/.

Monthly propagation charts between four USA regions and twelve
overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins.

Sunspot numbers for February 2 through 8 were 85, 39, 43, 37, 27,
24, and 28, with a mean of 40.4. 10.7 cm flux was 118, 111.1, 107,
102.7, 112, 107.2, and 97.2, with a mean of 107.9. Estimated
planetary A indices were 4, 6, 6, 6, 4, 12, and 10, with a mean of
6.9. Estimated mid-latitude A indices were 3, 4, 7, 6, 5, 10, and 9,
with a mean of 6.3.
NNNN
/EX