ARRL

ARRL Propagation Bulletin ARLP008 (2008)

SB PROP @ ARL $ARLP008
ARLP008 Propagation de K7RA

ZCZC AP08
QST de W1AW  
Propagation Forecast Bulletin 8  ARLP008
From Tad Cook, K7RA
Seattle, WA  February 22, 2008
To all radio amateurs 

SB PROP ARL ARLP008
ARLP008 Propagation de K7RA

No sunspots yet, and the Sun has been blank for seventeen days.  For
a week one sunspot was visible prior to the spotless period, and
that followed a twenty-day spotless run.  NOAA and the US Air Force
have predicted daily solar flux right at 70 recently, but bumps that
to 72 March 1, continuing into April.  This is a minor change, but
perhaps this signals that forecasters don't expect any more spots
during February.

NOAA also predicts low geomagnetic activity until February 28-29,
with the planetary A index at 5 through February 26, then 8, 20, 15
and 12 through March 1.  Geophysical Institute Prague predicts quiet
conditions February 22-26, quiet to unsettled February 27, and
unsettled February 28.

The days are getting longer, so openings should be longer on the
higher frequencies.  For instance, from California to Japan on
February 1, the 20 meter path would be open 2200-0100z.  On the last
day of this month the path should be open longer, 2130-0200z, but
signals weaker by about 10 db.  At the Vernal Equinox on March 20
that opening would stretch from 2100-0400z.

17 meters to Japan on February 1 would have an opening about
2230-0000z, but at the end of the month would lengthen to
2200-0100z, and signal levels barely lower.  By March 20 that 17
meter opening should stretch from 2130-0300z.  All of these times
and frequencies assume 0 sunspots.

Chuck Miller, N6KW noted that on Sunday in the ARRL DX CW Contest he
had a good 40 meter opening to Europe from his place in Seattle
during daylight, from 2300-0000z.  Stations worked were OK5R, TM9R,
IR4X, F8CMF and OM5ZW.  From Seattle to Europe last Sunday, this
wouldn't be unusual, although signals would be strongest 1-3 hours
later.

Kevin Seeger, WD0AVV of Corona, California wants assurance that this
bulletin will identify Cycle 24 sunspots as they appear, and also
needs a method to find out for himself what the polarity is.  Yes,
we will keep readers informed of new spots and identify them as
Cycle 23 or 24.

A way to check for yourself is to look at the magnetograms from the
SOHO spacecraft at,
http://sohowww.nascom.nasa.gov/data/realtime/mdi_mag/512/.  If you
see a sunspot with black on the right side and white on the left,
this is a Cycle 23 spot.  A Cycle 24 spot will lead with white on
the right and black on the left.  You can see this by searching the
archives for images from early February.  Go to,
http://sohodata.nascom.nasa.gov/cgi-bin/data_query and under image
type, select "MDI Magnetogram," select the "Images" option under
Display, and enter 2008-02-02 for Start Date, 2008-02-04 for End
Date, then click Search.  The result will be a series of images of
Cycle 23 spots.

Randy Wing, N0LD of Rose Hill, Kansas wrote that "it is interesting
to note" that when there were no sunspots, "I was working Ducie
Island on 10, 12, 15, 20 and 80 meters."  Very impressive, but check
out his nice antennas at, http://www.qrz.com/n0ld.

George Munsch, W5VPQ of San Antonio, Texas had comments about recent
160 and 75 meter discussions.  He writes, "The 160/75 meter
propagation conundrum arises because the F-layer is needed for
propagation and the D-layer must be weak or absent to minimize
absorption.  When both layers are weak or absent during these long
stretches of no sunspots, the bands aren't going to be very useful,
which has been my observation here in Texas, although domestic long
skip on 75 in the mornings has been pretty good.  The only problem
is that many of the stations heard are in small local cliques who
are accustomed to talking among themselves, and don't want to be
bothered with contacts to out-of-area 'intruders'."

George Coleman, AA4LR of Loganville, Georgia had an interesting
observation about this solar activity minimum we are experiencing.
He writes, "One thing I've noticed that separates this solar minimum
from others is the level of the solar flux. Seems like we've had
very, very few days of solar flux lower than 70. However, I seem to
remember at least from the solar minimum in the 70s and 80s that
solar flux got as low as 66, and stayed there for a considerable
period of time. I remember listening to WWV over a period of several
days, and finding that the solar flux levels were unwavering from
66."

I think George is right.  Solar flux hovers around 70 or above, but
doesn't go down to 66-68 this time.  For instance, May 21-30, 1996
the average solar flux was 66.7.  The average solar flux for all of
September and October 1996 was 69.3.  We are cherry-picking the data
here, but for the 7 days of July 18-24, 1996 the solar flux was
66.8, 64.9, 66.1, 65.4, 65.1, 66, and 66.7, an average of 65.9.

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://www.arrl.org/tis/info/propagation.html.  For a detailed
explanation of the numbers used in this bulletin see,
http://www.arrl.org/tis/info/k9la-prop.html.  An archive of past
propagation bulletins is at http://www.arrl.org/w1aw/prop/.  Monthly
propagation charts between four USA regions and twelve overseas
locations are at http://www.arrl.org/qst/propcharts/.

Sunspot numbers for February 14 through 20 were 0, 0, 0, 0, 0, 0 and
0 with a mean of 0.  10.7 cm flux was 70.6, 69.7, 70.3, 71.1, 71.2,
71.7, and 70.9 with a mean of 70.8.  Estimated planetary A indices
were 15, 10, 9, 5, 12, 12 and 7 with a mean of 10.  Estimated
mid-latitude A indices were 10, 8, 8, 3, 9, 10 and 5, with a mean of
7.6.
NNNN
/EX