ARRL

ARRL Propagation Bulletin ARLP007 (2008)

SB PROP @ ARL $ARLP007
ARLP007 Propagation de K7RA

ZCZC AP07
QST de W1AW  
Propagation Forecast Bulletin 7  ARLP007
From Tad Cook, K7RA
Seattle, WA  February 15, 2008
To all radio amateurs 

SB PROP ARL ARLP007
ARLP007 Propagation de K7RA

No sunspots appeared this week.  Solar flux was about the same as
last week.  The 45-day outlook for solar flux and planetary A index
from NOAA and the Air Force (see
http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html) on February 10
was predicting a flat solar flux of 70.  Then the following day this
was revised to show 72 for February 12-18, then 70 after that.  On
February 12 this changed to show 72 solar flux for February 13
through the rest of the 45 days.

February 10-13 we saw increased geomagnetic activity due to another
solar wind stream.  The planetary A index, calculated from a number
of mostly higher latitude magnetometers, was 18, 17, 11 and 12 over
those four days.  Alaska's college A index, measured near Fairbanks,
was 42, 31, 22 and 26, illustrating the increased geomagnetic
activity toward the poles in response to space weather.  Here at
mid-latitudes, where many of us live, the A index (measured in
Virginia) was 13, 16, 6 and 10.  That magnetometer is near 38.3
degrees north latitude, which is a little south and of course way
east of the Boulder site (at 40.1 degrees north latitude), where we
get the K and A index reported on WWV.

Jon Jones, N0JK of Wichita, Kansas reports some February E-skip
openings on 6 meters.  He writes, "Es tend to become scarce in
February, and March has the lowest occurrence of Es of any month."
On February 2 he worked XE2YWB in Central Mexico (DL82) at 2237z on
50.125 MHz with S7 signals.  The next day he worked K4EU in Virginia
via E-skip on 10 meters.  K4EU reported working stations throughout
the Midwest that day.

Ed Swynar, VE3CUI of Newcastle, Ontario took issue with a statement
in last week's bulletin about the absence of sunspots being great
for 160 meters.  He comments, "Such mythology could not be further
from the truth this year. The band has been MOST unremarkable this
season, to say the least, and it continues to languish away in the
doldrums. I thought that perhaps it was something at fault at my
end, however, many subscribers to W4ZV's Topband Reflector seem to
be of the same opinion."

Readers have sent similar reports about both 160 and 75 meters over
the past year.  It seems that low geomagnetic and sunspot activity
should be good for the lower frequencies, but perhaps it is not
always the case.

Over the past week many, many emails arrived from readers with a
link to an article in a daily business publication claiming that we
are on the verge of another Maunder Minimum, a decades-long period
of little or no sunspot activity that occurred roughly between the
years 1640 to 1710.  The article appeared with no byline, and it
quoted Dr. Kenneth Tapping, of the Herzberg Institute of
Astrophysics in Penticton, British Columbia.  This is the
observatory that supplies our daily solar flux values.  But I
thought the quotes sounded a little strange, and not like Ken.  Some
readers also felt this way.  As one wrote, "The article didn't quite
ring true," and "I have a fairly broad scientific reading list."

I sent an email to Ken, who responded that this has been a difficult
week for him.  A few weeks ago he received a phone call from a woman
who engaged him in "a long discussion involving possibilities
ranging from likely to not likely."  He wrote that the article
promotes something that is untrue, and "in no way do I support the
conclusions she assigned to me."

I think we can relax about any possible upcoming 70-year period of a
quiet Sun.  We cannot say that it could not happen, but in fact
there is nothing unusual about the current solar cycle minimum, and
really no known method of predicting such a period.

This weekend is the ARRL International DX CW Contest.  The
geomagnetic field is expected to be quiet.

Last weekend I watched an interesting DVD from the local library, a
1994 documentary titled "Picture of Light."  This has some nice
time-lapse long-exposure moving images of Aurora, taken in
Churchill, Manitoba, on Hudson Bay above 58 degrees north latitude.

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 7 through 13 were 0, 0, 0, 0, 0, 0 and
0 with a mean of 0.  10.7 cm flux was 70.8, 70.9, 72.2, 72.6, 72.1,
72.1, and 70.5 with a mean of 71.6.  Estimated planetary A indices
were 5, 4, 2, 18, 17, 11 and 12 with a mean of 9.9.  Estimated
mid-latitude A indices were 6, 3, 2, 13, 16, 6 and 10, with a mean
of 8.
NNNN
/EX