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The K7RA Solar Update


Thanks so much to Tomas Hood, NW7US, who wrote last week’s bulletin while K7RA was in California at dance camp. Tomas writes the weekly propagation column for CQ magazine, and he has an excellent Web site devoted to propagation. Tomas mentioned that the August 11 sunspot number of 66 is the highest recorded for Solar Cycle 24, but actually there were higher values recorded on May 4-5, when the sunspot number was 70 and 77, as you can see here. See also values from the current quarter. To see higher sunspot numbers, we must look back to the downward slide of Solar Cycle 23 on April 12, 2006 when the sunspot number was 79. The 2006 data is here.

Sunspot numbers and solar flux declined this week, with the average daily sunspot numbers down nearly 17 points to 36.1, and the average daily solar flux down 1 point to 83.5. In the previous week, the average daily sunspot numbers had risen nearly 33 points to 53. Sunspot numbers for August 12-18 were 50, 51, 31, 33, 39, 26 and 23, with a mean of 36.1. The 10.7 cm flux was 83.8, 83.7, 85.2, 85.6, 84.7, 81.1 and 80.3, with a mean of 83.5. The estimated planetary A indices were 4, 4, 3, 5, 7, 5 and 5. with a mean of 4.7. The estimated mid-latitude A indices were 3, 3, 2, 5, 4, 3 and 3, with a mean of 3.3.

New sunspot groups appeared on August 11, 13 and 16, but on Tuesday and Wednesday (August 17-18), total sunspot area was one-fifth what it was on August 16, less than one-seventh the area on August 14 and less than one-fourteenth the area of August 12. On August 12, 14, 16 and 18, the daily sunspot number was 50, 31, 39 and 23, and on August 19 it was 11, which is the minimum non-zero sunspot number.

Projections for solar flux over the next 10 days, August 20-29: 78, 78, 77, 77, 79, 80, 82, 84, 82 and 81. Predictions for planetary A index over those same days are 5 on August 20-23, 6 on August 24, 12 on August 25-26 and 5 on August 27-29. Geophysical Institute Prague predicts quiet conditions for August 20-22, quiet to unsettled August 23 and unsettled August 24-26.

Greg Andracke, W2BEE, of Pine Plains, New York, says he will visit St Vincent and the Grenadines in the Caribbean in mid-December, and wants to know what night time propagation might be like on 20 and 30 meters. Running some numbers with W6ELprop shows that the local sunset time is 2138 on December 15. Propagation back to anywhere in the USA doesn’t look promising after dark, but paths to South Africa and South America look good.

Thanks to David Moore of Morro Bay, California, and Mark Downing, WM7D, for sending a couple of articles on a possible explanation for weak solar activity. The articles are here and here.

Bob Forsman, WK5X, of Stuart’s Draft, Virginia, commented about an item in the August 6 bulletin. “KA3JAW’s reception of Channel 2 from Ontario probably had nothing to do with the CME. It’s likely just garden-variety late-season sporadic-E, in my opinion; I’m pretty sure that you realize this, also. 1300 miles is close to the maximum distance possible via single-hop, but it isn’t terribly unusual. The MUF of the E-layer was likely around 58-60 MHz at the mid-point.”

Dean Lewis, W9WGV, of Palatine, Illinois wrote: “While I realize this is old news, it might at least be worth the perspective. Being used to 20/30/40 meter propagation, I didn’t have any particular appreciation for contacts I’d made on 6 meters. Having just purchased a new rig, I thought I’d give it a try on 6 meters during the June VHF QSO Party. Without a 6 meter antenna, I managed to tune up my 66 foot end-fed 40 meter wire through a short length of coax as something of an off-center resonant feedline dipole.

From our location 25 miles northwest of Chicago, I worked 11 states with the rig’s 10 W (CW) output: Alabama, Florida, Georgia, Illinois, Massachusetts, Mississippi, New Hampshire, South Dakota, Texas, Utah and Wisconsin (I QSL 100 percent with a self-addressed, stamped envelope; the return cards have all arrived). Family events over the weekend limited my air time; I could have done more, I’m sure. Oh, the antenna is indoors (we have a typical townhouse with CC&Rs). Now I understand why they call it ‘the magic band.’”

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 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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