The K7RA Solar Update
This weekend is the CQ WPX CW Contest and conditions may be a little rough. Our current sunspot group 1072 has reached the Sun’s western horizon and is shrinking, and to top it all off, what looked like a possible emerging spot on Wednesday was not to be.
There is a stiff solar wind heading toward Earth, and the predicted planetary A index for May 28-31 is 20, 20, 22 and 15. The predicted solar flux is 73 for May 28-29, 75 for May 30-June 3 then 80, 78, 76, 75 and 70 for June 4-8. This prediction is from NOAA and USAF on May 27, but on May 26, they predicted a solar flux of 76, 78, 80, 82, 82, 79, 80 and 80 for May 28-June 4.
Sunspot numbers for May 20-26 were 12, 15, 20, 23, 17, 16 and 11, with a mean of 16.3. The 10.7 cm flux was 68.8, 70.9, 72.5, 74.5, 72.6, 73.2 and 72.4, with a mean of 72.1. The estimated planetary A indices were 9, 5, 4, 2, 2, 5 and 6, with a mean of 4.7. The estimated mid-latitude A indices were 9, 4, 2, 0, 0, 4 and 5, with a mean of 3.4. Geophysical Institute Prague predicts a minor geomagnetic storm for May 28, active conditions for May 29, quiet to unsettled May 30, unsettled May 31 to June 1, quiet to unsettled June 2 and quiet conditions June 3.
The STEREO spacecrafts currently view about 89.5 percent of the Sun. A month from now they will see 90.3 percent; in two months, the coverage will be 91.4 percent, and it will be 92.8 percent in three months. Currently, they see a bright spot about 30 degrees west of the Sun’s eastern horizon, but this doesn’t appear to be a new sunspot group -- at least not yet.
Thanks to Scott Bidstrup, W7RI, for the heads up on an interesting article from Scientific American on our Sun’s odd behavior and low activity.
Julian Moss, G4ILO, has been using WSPR (Weak Signal Propagation Reporter) to search for marginal or unknown propagation paths. He writes: “With the sporadic-E season starting, I thought that I would try WSPR on 10 meters to spot band openings. What has been surprising is the consistent paths between stations in Faroe Islands and Iceland, and the UK and Western Europe. The paths were occurring even during the period of no sunspots and occurred when no other long distance propagation was being reported between WSPR stations anywhere else. I would have not expected the F2 MUF to be high enough to support propagation at that time and that latitude. I don’t think many people have regularly tried 10 meters at other times, so I don’t know if this has been observed before. I haven't found any actual activity on 10 meters at this time, but of course the Faroes and Iceland are not in parts of the world with a lot of amateurs.” Julian has a nice map illustrating this on his blog. He also has a nice description of how WSPR works.
Bob Brown, NM7M, a true radio propagation guru passed away this week at age 87. In addition to teaching physics at University of California at Berkeley, he wrote The Little Pistol’s Guide to HF Propagation.
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.