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The K7RA Solar Update


Last week saw another brief sunspot appearance followed by a quick fade. This was an old Solar Cycle 23 spot -- number 1001 -- resulting in a sunspot number of 12 for September 11. Sunspot numbers for September 11-17 were 12, 0, 0, 0, 0, 0 and 0 with a mean of 1.7. The 10.7 cm flux was 66.9, 66.3, 66.4, 66.8, 67.5, 69.4 and 67.1 with a mean of 67.2. Estimated planetary A indices were 2, 2, 0, 6, 15, 9 and 3 with a mean of 5.3. Estimated mid-latitude A indices were 1, 0, 0, 4, 11, 7 and 3 with a mean of 3.7.

Sunspot 1001 was similar to other recent spots that made only a weak, brief appearance. On September 18, Belgium's Royal Observatory produced a report titled "The Sunspot Number Clarified" that talks about these weak spots making brief appearances and the issues they raise during a sunspot minimum. It says that some "human arbitration" is required to determine what is counted as an observed sunspot, and they base this on data from multiple locations. If some locations see no spot on the day in question, the sunspot can still be counted if it is seen by multiple other locations. You can read about it here -- click on the report title dated September 18, then click on the link marked "Handling very low activity levels." You can download the article, along with all other parts of the report.

For the near term, nothing indicates any emerging sunspots. The geomagnetic indicators should remain quiet with a planetary A index of 5 until the end of the month. From September 30-October 2, the planetary A index is expected to be 8, 30 and 8. Eight is a low number, but 30 indicates a geomagnetic storm, probably expected from a recurring coronal hole spewing a strong solar wind.

While the lack of sunspots is discouraging, the lack of geomagnetic activity is welcome. In times past, we had good sunspot activity, but constant solar wind disturbed geomagnetic conditions and making HF propagation very difficult. On Tuesday, September 23, scientists from the Ulysses International Solar Mission will participate in a NASA teleconference that will talk about the solar wind now being at a 50-year low. The teleconference begins at 12:30 PM EDT (1630 UTC) and you can hear it live. You can see visuals that will accompany the presentations here

Solar flux values (a measure of 2.8 GHz radiation detected by a parabolic antenna aimed at the sun in Penticton, British Columbia) were a bit higher this week, although in normal times, any flux value under 70 is considered quite low. The September 16 solar flux was 69.4, the highest it has been since May 18, 2008.

This week we saw a post by John Sahr, WB7NWP, a professor of geophysics and electrical engineering at the University of Washington. He noted, "I've been watching solar wind data daily for nearly a decade, and I have never seen such a long period of such quiescence."

This Monday, September 22, marks the autumnal equinox, the first day of the fall season. This is generally considered a good time for HF communications, and the Sun's energy shines equally on the northern and southern hemispheres. When I use a propagation prediction program to compare next Tuesday with the same date three months ago, there are some differences. For September from Seattle to New Zealand, 15 meters offers a reasonable opportunity, but no possibility in June. Seventeen meters has a longer opening in September, although the June numbers look good later in the evening. Twenty meters is good from 0330-0530 UTC in September, but in June the opening ends 30 minutes earlier and signals aren't as strong. In September, 30 meters is very strong all night long from 0500-1530 UTC, but in June the openings are brief, at 0430-0630 UTC and again from 1400-1500 UTC.

Brian Webb, KD6NRP, of Ventura County, California, says that despite the low solar activity, he's been having a great time on HF running fewer than 100 W with a modest antenna system on 160-10 meters. He has only been on HF since February 2007, and has made a long list of contacts all over the world.

Similar comments came from Mark Mokoski, K1PU/VK2IFH, of Higganum, Connecticut, who decided to rework DXCC and WAS with his new call (he was WA1ZEK for 30 years). He is using 100 W with an 80 meter dipole and a trap vertical; over the past two months, he has worked 93 countries, mostly on 30 and 40 meters. He didn't mention it in his e-mail, but I noticed here that he has free ham radio software he's written, including a telnet client for DX cluster operation.

Last week's bulletin mentioned PY2ZX in Jundai (a town in Brazil), but an e-mail from Paulo de Tarso, PU2PTH, in Sao Paulo, Brazil, mentioned that Jundai is in Southeast Brazil, not Northeast. There are actually several places named Jundai in Brazil, but PY2ZX is not in the Jundai in Northeast Brazil near Recifé, but instead not far from Paulo in Sao Paulo.

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 in The ARRL Letter. 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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