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The K7RA Solar Update

07/29/2011

Sunspot activity dipped over this past week, but now it on its way back up. On July 20, five sunspot groups were visible, but on July 21, only groups 1251, 1254 and 1259 remained. On July 24, new sunspot group 1260 appeared, and the next day, 1251 disappeared. On July 26, groups 1254 and 1259 went away, and new sunspot group 1261 arrived. The next day, another new group -- 1262 -- appeared, and on July 28, two new sunspot groups -- 1263 and 1264 -- appeared. On July 28, the total area of visible sunspots was greater than it has been since the end of May.

Sunspot numbers for July 21-27 were 56, 54, 41, 46, 38, 30 and 54, with a mean of 45.6. The 10.7 cm flux was 96, 92.4, 88.2, 86.2, 87, 93.5 and 99.3, with a mean of 91.8. The estimated planetary A indices were 12, 10, 8, 4, 12, 5 and 4, with a mean of 7.9. The estimated mid-latitude A indices were 10, 10, 6, 3, 10, 5 and 2, with a mean of 6.6. The average daily sunspot numbers for the week July 21-27 declined nearly 47 points, a little more than 50 percent, to 45.6. The average daily solar flux declined more than 6 points to 91.8.

The latest forecast for solar activity has been revised from what was reported in this week’s ARRL Letter. The forecast shows predicted solar flux at 110 on July 29-August 4, 100 on August 5, 95 on August 6-7, 98 on August 8 and 100 on August 9-16. It also shows the planetary A index at 5 on July 29-30, 12 on July 31-August 1, 7 on August 2, 5 on August 3-4, followed by 12 again on August 5-7, 8 on August 8-11. Geophysical Institute Prague predicts quiet conditions on July 29, quiet to unsettled July 30, unsettled July 31 and August 1, then quiet to unsettled August 2 and quiet again on August 3-4.

Kent Reinke, KL1V, reports some interesting VHF propagation on Thursday, July 28: “I live in Valdez, Alaska, and today I had a very strange opening while I was driving home from Dawson City, Yukon, Canada. I was 30 miles northwest of Tok, Alaska on the “Top of the world highway,” and while trying to pick up a local FM station from Tok, I was surprised to hear several stations full quieting with slow fade. After listening to them a few minutes, I found out they were all from Edmonton, Alberta, Canada, which is a distance of about 1235 miles. There are several mountain ranges between where I was and Edmonton. Between the fades, the stations sounded like I was in Downtown Edmonton. I only had my 2 meter radio with a mag mount antenna, but I did try a few calls on 146.52 simplex, but no one heard me. The opening lasted 45 minutes and I was not sure if it was ducting or sporadic-E. Next time I will have the 6 meter along,”

Thanks, Kent. Very interesting.

Bear Carson, AC7HI, lives in Spokane in Eastern Washington State. He recently wrote to ask about a “blackout” of radio signals he noticed. I sent his message to Randy Crews, W7TJ, who lives about 8 miles southeast of AC7HI. Randy had these comments: “You know, if I could pick one month out of the year that I believe is the worst for propagation in the Pacific Northwest, it would be July. Not so much static, but flat east/west propagation and high summer D-layer absorption. There have been exceptions over the years, but July seems to always be the low point of the summer. Recently, I noticed that all HF propagation has really been down in the past few days, even in spite of increasing solar flux and sunspots, plus a quiet geomagnetic field, low dynamic pressure and solar wind, plus magnetic field oriented north, and small auroral ovals. The big reason I can see is high x-ray flux, which will negate all the propagation positives just mentioned. What I noticed was four months of just stellar propagation starting in mid February of this year and going until about mid June.

“Recently, two DXpeditions -- ST0R and VK9HR -- have been extremely difficult to copy. The VK9 Group is on an island surrounded by salt water, and compared to the T31A group in April from Canton Island, their signal on all bands has really been marginal. With the recent increase of solar flux, they should be S9 all the time. So I would attribute things to the lower solar flux vs what we observed this last spring, high D level absorption and very high levels of x-ray flux. I believe that in spite of all the satellites and scientific equipment, propagation is still immensely complex.”

Thanks, Randy!

Often I get e-mail from non-hams who have heard some piece of contemporary folklore about threats to Earth from giant solar flares or mysterious planets. A recent article covers this well. Thanks to Howard Lester, N7SO, for the heads-up.

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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