ARRL

ARRL Propagation Bulletin ARLP008 (2011)

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 25, 2011
To all radio amateurs 

SB PROP ARL ARLP008
ARLP008 Propagation de K7RA

The average solar flux was nearly unchanged this week, up just 0.3
point to 103.8, while the average daily sunspot number was down 4.9
points to 65. Sunspot groups 1161 and 1162 -- which brought so much
activity last week -- have now rotated across our Sun's western
horizon, but new sunspot group 1163 has now emerged over the eastern
limb.  For Thursday, February 24, we saw a sunspot number of 23. The
solar flux was 88.9, planetary A index was 3 and the mid-latitude A
index was 0.

The outlook from NOAA/USAF shows 90, 88 and 88 for February 25-27,
then 86 on February 28 through March 4, 95 on March 5, 100 on March
6-8, 105 on March 9 and rising to 110 on March 10-15. The predicted
planetary A index for February 25-March 2 is 7, 8, 8, 15, 12 and 8,
then 5 on March 3-6, and 7, 8, 8, 7 and 5 on March 7-11. Geophysical
Institute Prague expects quiet to unsettled conditions for February
25-26 and quiet conditions on February 27 through March 3.

The predicted geomagnetic storm just prior to last weekend's DX
contest did not persist, lasting only half a day through February
18. It was triggered by a flare on February 15. Bob Marston, K6TR,
sent a link to a high definition video of the flare, as seen through
the Solar Dynamics Observatory. It can be viewed on YouTube at,
http://www.youtube.com/watch?v=IJViaJ_kgZ0.

Note that you can select resolution of the image by clicking on the
360p on the lower right and can run it as high as 720p. It takes
some time to load, varying dependent on your Internet connection
speed. Best to just let it load, then run it again to actually watch
it.

Dean Straw, N6BV, observed last Friday that the "latest solar wind
sequences show that the Bz field was strongly north-directed (rather
than south-directed) from 05 to 10 UTC Feb 18, so we probably dodged
the big bullet for this ARRL DX CW weekend." He is referring to an
element of the IMF, or interplanetary magnetic field. When Bz points
south, our planet is vulnerable to flares and resulting solar wind,
but when Bz points north, we tend to be protected.

Carl Luetzelschwab, K9LA, has an interesting and informative column
on 10 meter sporadic-E propagation in the current issue of
WorldRadio Online. Carl mentions downloading N6BV's presentation on
sporadic-E titled, "HF Propagation and Sporadic-E, A Case Study:
WRTC 2010."

Bill Collins, KB1MSJ, of Boylston, Massachusetts, is excited about
openings on 10 meters. He wrote: "On Friday, February 18, there was
a 10 meter band opening here on the East Coast. I was able to talk
to Aruba, Brazil and El Salvador, all with only 25 W of power on a
homebrew 10 meter antenna. I have been waiting for this to happen
for years, as I only have my Tech license (working on General) and
have an old 10 meter radio".

Elwood Downey, WB0OEW, of Tucson, Arizona, wrote: "Just wanted to
mention you seem to have missed the highest actual 10.7 cm flux
reported from Penticton for all of last week. On February 13 at
1800, it was 125.7. The value you report for February 13 -- 106.8 --
was reported two hours later at 2000. Normally I wouldn't bother to
mention it, but this was higher than any value you reported for the
entire week and is something for the record books."

Yes, I saw that, but only the local noon number is the "official"
number for the day. Elwood is talking about the numbers as they are
reported directly from Penticton. Note that there are three readings
per day, and the local noon number is at 2000. NOAA rounds off the
solar flux noon reading to the nearest whole number, and reports it
at, http://www.swpc.noaa.gov/ftpdir/indices/DSD.txt.  I do like to
look at the morning and afternoon numbers though to try to spot
trends.

Sometimes NOAA will report a lower value for the day than the noon
reading at Penticton. This is if the receiver at Penticton was
overloaded, and the value is regarded as anomalous. But I don't have
any way of knowing when that receiver is overloaded. My only clue is
when NOAA reports a lower value.

In Propagation Forecast Bulletin ARLP006 we mentioned Joan Feynman
and erroneously reported that she is physicist Richard Feynman's
daughter, when in fact she is his sister. Thanks to Walt Knodle,
W7VS, Michael A. Gottlieb and Gregory Andracke, W2BEE, for the
correction. Greg is a filmmaker and mentioned that he met Richard
Feynman while working on a documentary with Bill Moyers on the 45
year anniversary of the atomic bomb. Michael A. Gottlieb (who is not
a ham) runs a website devoted to The Feynman Lectures on Physics. He
also published the book Feynman's Tips on Physics: A Problem-Solving
Supplement to the Feynman Lectures on Physics. He works in the
Caltech Physics Department and is editor of two editions of the
Feynman Lectures on Physics.

Another correction, this time from last week's bulletin, we mistyped
Bob Marston's call sign (K6TR) as K6TW. We got a nice note about
this from Tim Goodrich of Torrance, California, the proud owner of
new vanity call K6TW, which he has held for just one month.

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://mysite.ncnetwork.net/k9la/index.html.

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 17-23 were 51, 101, 79, 103, 60, 34 and
27, with a mean of 65. The 10.7 cm flux was 110.9, 124.8, 109.4,
104.6, 96.7, 90.9 and 89.3, with a mean of 103.8. The estimated
planetary A indices were 2, 17, 5, 7, 7, 1 and 4, with a mean of
6.1. The estimated mid-latitude A indices were 5, 15, 3, 6, 7, 1 and
1, with a mean of 5.4.
NNNN
/EX