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The K7RA Solar Update


Two new sunspot groups appeared in the last week -- groups 1087 and 1088. Group 1088 lasted just one day -- on July 13, 2010 -- with a relative area of 10 (millionths of a solar hemisphere). Sunspot group 1087 had a relative area from July 9-15 of 30, 100, 120, 130, 70, 100 and 60. Sunspot numbers for July 8-14 were 11, 12, 18, 25, 22, 28 and 16, with a mean of 18.9. The 10.7 cm flux was 75.6, 80, 79.9, 82.6, 80, 78.5 and 77.7, with a mean of 79.2. The estimated planetary A indices were 3, 5, 2, 5, 5, 3 and 11, with a mean of 4.9. The estimated mid-latitude A indices were 2, 4, 0, 2, 2, 1 and 7, with a mean of 2.6. The average daily sunspot numbers this reporting week (July 8-14) rose 2.9 points to 18.9, and average daily solar flux was up 6.4 points to 79.2.

The predicted solar flux for July 16-23 is 76 on each day, then 74 on July 24-27; this is lower than recent forecasts predicted. The predicted planetary A index for July 16 is 10, followed by 5 for each day through July 22. The next rise in planetary A index is July 23-28, when it is predicted to be 18, 12, 10, 8, 15 and 10. Geophysical Institute Prague predicts quiet geomagnetic conditions July 16-21, and quiet to unsettled on June 22.

On Wednesday, July 14 there was an interruption in the portion of the STEREO image that faces Earth, but by early Thursday morning it was restored. On July 18 around 1000, the STEREO mission coverage will reach 91 percent of the Sun’s surface. In February 2011, the Solar Dynamics Observatory will provide the data to the STEREO online display that appears around the 0 degree meridian, and solar coverage should be at 100 percent. Due to movement of the STEREO craft, as the gap closes on the far side, a new one facing Earth will begin in January 2011. Eventually, the two spacecraft will work their way around the Sun and return to their original position by 2024.

In another example of sporadic-E propagation, Erik Beck, who I think might be N7FYO, reports” “As I was driving outside Providence, Rhode Island, at about 9 AM, I was able to pull in loud and clear on 90.1 MHz, WXVS, in Waycross, Georgia. By far the longest DX FM station I have encountered! This with a car radio and an in- window antenna!” WXVS runs 79 kW with a tower just north of the Okefenokee Swamp, around 1000 miles from where Erik was driving.

Vince Varnas, W7FA, of Aloha, Oregon, wrote to say this about E-skip: “As the sporadic-E skip distance on the lower frequencies shortens, the E-skip on higher (VHF) frequencies appears and is longer in distance (single hop). Thus, very short skip on 10 meters means longer skip on 6 meters, and probably E-skip on 2 meters at a still longer distance.” He says that one way to spot 6 meter openings is to watch 10 meters.

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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