The K7RA Solar Update
Solar activity retreated again this week, with the average daily sunspot numbers declining 8.7 points to 49.7, while the average daily solar flux was down nearly 20 points to 97.2. Sunspot numbers for November 1-7 were 48, 34, 35, 46, 47, 61 and 77, with a mean of 49.7. The 10.7 cm flux was 98.4, 96.5, 93.3, 95, 96.6, 98.7 and 101.7, with a mean of 97.2. The estimated planetary A indices were 17, 5, 3, 2, 2, 4 and 10, with a mean of 6.1. The estimated mid-latitude A indices were 17, 5, 2, 1, 2, 4 and 10, with a mean of 5.9.
The latest forecast shows solar flux at 105 and 110 on November 9-10, 115 on November 11-17, 100, 110 on November 18-20, 105 and 100 on November 21-22, 105 on November 23-24 and back down to 100 on November 25-26. The solar flux values then drop below 100 on November 27-December 2. The planetary A index forecast predicts an index of 9 on November 9, 7 on November 10-12, 5 on November 13-18, 8 on November 19, and back down to 5 on November 20-December 4, and rising to 10 for December 5-8.
Currently, the Sun is peppered with a few weak spots, but there have been a couple of new sunspot groups each day, beginning on November 3. There was one new spot on November 3, November 4 had two, then two more on November 5, one on November 6 and another on November 7, and two new ones on November 8.
NASA has once again tweaked its forecast for the smoothed sunspot number at the peak of Solar Cycle 24 next fall: On October 2, it predicted a sunspot number maximum of 75 in fall 2013, and on November 2, it was changed to 73.
Scott Wright, K0MD, of Rochester, Minnesota, shared some brief observations on conditions during the CQ WW DX SSB Contest (October 27-28, two weekends ago): “I did not find the band openings nearly as good this year as last year. Ten meters was very good, but not as good as 2011. Propagation was down on 40 meters, with lower country totals from the Midwest than I saw last year. On 160 meters, it was not very good, but no surprise there, given it is October.”
Scott noted the better propagation during the same contest last year. This year, the average daily sunspot number for the 10-day period ending on Sunday, October 28 -- the last day of the contest -- was 79.8. But for the same period last year -- ending on Sunday, October 30, 2011 -- the average daily sunspot number was 111.6, quite a bit higher, 40 percent higher, in fact.
Max White, M0VNG, of Worcester, England, sent this article about a coronal hole and a disastrous solar wind that occurred in January 1994. We can check an archive of geomagnetic indices to get a sense of what the effect on Earth was. Note there are days in January of that year when readings from the magnetometer near Fairbanks, Alaska (the college A index) that have asterisks instead of numbers. This is what we see occasionally when the magnetometer is completely overloaded with energy, and cannot produce any sort of meaningful results. We can see there was a lot of geomagnetic activity that year. I would like to refer to propagation bulletins from January 1994, but unfortunately the ARRL’s online archive doesn’t begin until January 1995. If anyone has copies of the propagation bulletin prior to 1995, please contact me. Perhaps you have an old hard drive from a personal computer used for packet radio 20 years ago?
Carl Luetzelschwab, K9LA, has some great propagation resources on his website. He has download links for free PDF copies of both NM7M propagation books, as well as a slide presentation showing an update on Solar Cycle 24. If you don’t have Microsoft PowerPoint to watch the slides, you can download a free reader here.
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.