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The K7RA Solar Update

02/25/2011

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. 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 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. 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, “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 here. 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.

Two weeks ago, 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.

All times listed are UTC, unless otherwise noted.

Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. You can find a guide to articles and programs concerning propagation here. Check here and here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.



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