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 Previous: ITU to Mark 100 Years of International Radio Regulations |  Next: New Section Managers Gather to Learn at ARRL Headquarters |
SEATTLE, WA, Oct 20, 2006 -- Sunspot numbers this week were zero on every day. In fact, zero was the sunspot number for eight days in a row: October 11 through 18. On October 19 a single sunspot appeared, Sunspot 917, in the center of the solar disc as seen from Earth. This resulted in a sunspot number of 14. Due to the way sunspot numbers are calculated, there are no sunspot numbers from 1 through 10 -- only zero for the minimum and then 11 for the next number. Judging from numbers 10 years ago at the last solar minimum, we should observe longer periods of no sunspots -- several weeks in a row, or perhaps a month or more.
In late 1995 we began to see short stretches of time with no spots. Then there were 12 days in a row, February 3 through 14, 1996, that were spotless. We began to observe one to two-week stretches with zero spots, except for one or two days in the middle. May 18-21, 1996, had no spots, but the next two days recorded 11 and 12, respectively. But there were no spots May 24 through 31. In fall 1996 we saw a really long stretch, September 9 through October 24, 1996, with only two days in that period with recorded sunspots. September 13 through October 20 had no spots at all. After this, the spotless days were less and less common, with some strings of 7 to 10 spotless days in early 1997.
By the fall of 1997, things were jumping again. October 1996 had an average daily sunspot number of only 2.3, October 1997 was 33.5, October 1998 was 77, October 1999 was 167.7, October 2000 was 138.9, and the average daily sunspot number in October 2001 was 197.4.
So far October 2006 has an average daily sunspot number of 13.1, so we have a bit to go before we see a typical bottom-of-the-cycle month of no sunspots. The predicted sunspot minimum is still about six months away.
Just because there are no sunspots, does that mean HF radio is dead? No, in fact it is better for 160 and 80 meters. But even higher frequencies will have openings to somewhere, although not as frequently as during periods of higher sunspot activity.
John Plenderleith, 9M6XRO, in Eastern Malaysia wrote to say that last Friday October 13, the third day in a row with zero sunspots, he worked OM3EY in the Slovak Republic on 12 meter CW, and they moved the QSO to 10 meters. Conditions weren't very good, but signals were able to be copied. Then as John put it: "Suddenly -- bam -- the band was wide open, and in the next 2-1/2 hours I worked 283 stations from all over Europe, a few in the Middle East, J28JA and a solitary JA. For much of the time I had 18 dB attenuation in on my FT-1000MP and signals were still S9 on the meter -- a solid wall of stations!" He reports the opening ended at 8:35 PM local time, about an hour and a half after local sunset. "It brought back memories of 1957/58 when I was an SWL and 10 meters was wide open every day!" he said.
John continues: "Just goes to show, even at this point in the cycle, it pays to go on the bands and fill up those empty frequencies -- you never know what might happen!"
Rick Fleeter, K8VK, of Reston, Virginia has been a ham since 1963, when he was nine. He likes the quiet conditions that come with lower sunspot activity. He writes:
"I find low sunspot cycles the best times for radio work in HF. I'm not just talking about the top bands. There is not much difference between sunspot activity and simple every daytime solar excitation of the ionosphere. Except that at near zero sunspots, the progression of propagation during the day is completely rhythmic with the daily clock, and predictable. The longer wavelength bands are much quieter at night when the sun is quiet, and even with no sunspots, 20, 15, even 10 meter openings are quite regular during the day. Plus it seems like a less opaque ionosphere eliminates QRM from nearer stations (QRN as well does not propagate so well from nearby sources, which is most of it), so the DX which is there, is easier to hear."
This weekend we could have more days with zero sunspots, or at a maximum, sunspot numbers from 11-15. A solar wind stream is expected to cause active geomagnetic conditions today, October 20, with the October 20-23 planetary A index predicted at 20, 13, 8 and 5. Geophysical Institute Prague predicts declining geomagnetic activity, with active conditions on October 20, unsettled to active on October 21, unsettled October 22, quiet to unsettled October 23, unsettled October 24, and quiet conditions on October 25-26.
Eric Hall, K9GY of Lansing, Illinois, urges readers to participate in the Illinois QSO Party and the Worked All Germany Contest this weekend. In a week many hams will begin the CQ World Wide DX Contest (Phone) contest. Current predictions show planetary A index for October 27-29 of 12, 25 and 8. The Saturday number of 25 looks a little rough.
If you work the German contest this weekend, good times to check the different bands depend on your location.
From Boston, 80 meters looks promising from 2030-0800 UTC, with best bets around 0000-0530 UTC, 40 meters 1900-0200 UTC and 0430-0930 UTC. 20 meters looks good 1200-1900 UTC, and 15 meters could possibly be open 1230-1800 UTC, with the best bet around 1500-1630 UTC. All of this assumes a sunspot number of 11, which may be a bit optimistic.
From Atlanta to Germany, 80 meters looks good 2130-0730 UTC, with best signals around 0000-0600 UTC. Try 40 meters 2130-0330 UTC, or 0600-0930 UTC, with best signals around 2200-0200 UTC. 20 meters looks good 1330-1830 UTC. Slim chance of any 15 meter opening, but best chance is around 1430-1700 UTC.
From the center of the continental United States, Germany looks best on 80 meters 0030-0700 UTC, and 40 meters 2230-0330 UTC and 0700-0930 UTC. 20 meters is most promising 1430-1900 UTC and 15 meters possibly, but not likely, 1600-1730 UTC.
From North Texas, 80 meters 0100-0630 UTC, 40 meters 2300-0930 UTC, 20 meters 1330-1730 UTC, with signals declining over that period, and possibly again around 1930 UTC. Unlikely but possible is 15 meters 1430-1900 UTC.
From Chicago, 80 meters 2330-0700 UTC, 40 meters 2130-0230 UTC and 0700-0800 UTC. Check 20 meters 1500-1800 UTC.
Salt Lake City, 80 meters 0100-0700 UTC, 40 meters 0700-1000 UTC and 2300-0500 UTC. Check 20 meters 1530-1900 UTC.
From Los Angeles, 80 meters 0100-0800 UTC, best around 0330-0500 UTC. 40 meters 0030-0800 UTC and 20 meters 1500-1630 UTC.
From Seattle, 0000-0730 UTC on 80 meters, and on 40 meters, 2200-1030 UTC, 1200-1300 UTC and 1430-1630 UTC. Check 20 meters 1630-1800 UTC.
For More Information
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page and the article "The Sun, the Earth, the Ionosphere: What the Numbers Mean, and Propagation Predictions," by Carl Luetzelschwab, K9LA. An archive of past bulletins is on the ARRL Web site. The propagation charts that formerly appeared in QST now are available on the QST Propagation Charts page on the ARRL Web site.
Weekly Sunspot Numbers
Sunspot numbers for October 12 through 18 were 0, 0, 0, 0, 0, 0 and 0, with a mean of 0. The 10.7 cm flux was 73.6, 73.3, 72.4, 71.1, 69.5, 69.6, and 69.5, with a mean of 71.3. Estimated planetary A indices were 5, 24, 18, 10, 8, 2 and 4, with a mean of 10.1. Estimated mid-latitude A indices were 3, 15, 12, 9, 7, 2 and 2, with a mean of 7.1.
Amateur solar observer Tad Cook, K7RA, 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. Readers may contact the author via e-mail.
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