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The K7RA Solar Update


Solar activity was down this week, with the average daily sunspot number at 49.6, less than half last week’s figure. The average daily solar flux dropped 22 points to 97, and geomagnetic activity was quiet also. Sunspot numbers for March 21-27 were 60, 54, 56, 45, 56, 41 and 35, with a mean of 49.6. The 10.7 centimeter flux was 106.1, 100.9, 98.2, 96, 92.6, 92.4 and 93, with a mean of 97. The estimated planetary A indices were 12, 4, 11, 5, 4, 3 and 14, with a mean of 7.6. The estimated mid-latitude A indices were 11, 2, 10, 6, 3, 2 and 9, with a mean of 6.1.

The predicted solar flux is 95 and 100 on March 28-29, 105 on March 30-31, 110 on April 1-3, 115 on April 4, 120 on April 5-7, 125 on April 8-10, 120 on April 11-13, 115 on April 14, 110 on April 15, and then it drops below 100 for April 20-24. The predicted planetary A index is 22, 18 and 8 on March 28-30, 5 on March 31-April 22, then 8, 18, 15 and 8 on April 23-26, and dropping down to 5 through the end of April and into the first week in May.

Lee Gordy, W4KUT, of Cartersville, Georgia, wrote to say he just finished reading Carl Luetzelschwab’s article “The Sun and the Ionosphere” (in the March 2013 issue of QST) for the third time: “For me, it’s consoling to know that knowledgeable professionals such as Carl Luetzelschwab are having exciting difficulties rounding up Ol’ Sol’s secrets. There’s a fine and mystical line between prophesy and prognosis, and the even bigger consolation prize I’ve taken away from Carl’s informative writings is a closer understanding of songwriter Joni Mitchell’s wonderful composition, Both Sides, Now: ‘It’s cloud illusions I recall, I really don’t know clouds, at all.’ Regarding the Sun, we can literally see ‘both sides now.’ And it just seems like the more we know about it, the less we really know! I was there for Solar Cycle 19. It was mystical and magical, and I have every hope that I’ll experience a like ionospheric folly before I send my final SK. Who knows, maybe this cycle will have another peak, and we’ll hear non-stop, worldwide 10 and 6 meter activity. In the meantime, it’s fun to try and outguess solar mojo. It’s a big part of the infectious excitement and thrill of Amateur Radio.”

Lee must be referring to the Solar TErrestrial RElations Observatory project, or STEREO, which does allow us to observe both sides of the Sun, with real time images, too, updated every few minutes.

Bill Tynan, W3XO, of Kerrville, Texas (grid square EM00kd) wrote: “March 15’s coronal mass ejection apparently caused a major north/south opening on 6 meters. On Sunday, March 17 at 2122, I worked HC5VF; he was S-9 with 50 W. I did not hear any Central American stations, so my conclusion is that it was via F2, not multi-hop Es. I rule out trans-equatorial propagation (TEP), as Ecuador is above the magnetic equator. “Then, beginning from 2154 to 2256, I worked several Argentinean stations. I also heard a Uruguayan station, but did not work it. These could have, of course, been TEP since they are south of the geomagnetic equator. But since they followed so closely on the Ecuadorian station, it makes me wonder.”

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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