[South Florida DX Association] ARLP008 Propagation de K7RA

Fri Feb 25 16:11:10 EST 2011

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 at arrl.net <mailto:k7ra at 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