The K7RA Solar Update
The data at the end of last week's bulletin showed daily sunspot numbers from April 16-22 as six zeros, then 11. In fact, every day was at zero until April 21, when it was 11; it moved again to zero the next day, April 22. We had just as many zero sunspot days -- and only one day with a sunspot -- but we saw the sunspot on Tuesday, April 21, not April 22.
We had two additional days with a sunspot this week, Wednesday and Thursday, April 29-30. The sunspot number was 15 and 12, respectively, on those days. But this was another old Solar Cycle 23 sunspot, and it appeared near the western limb. By today, it may have either faded away completely or rotated out of view, May 1. The data at the bottom of our bulletin shows seven days, Thursday through Wednesday for the reporting week, so the sunspot number of 12 for Thursday will appear in next week's data.
Sunspot numbers for April 23-29 were 0, 0, 0, 0, 0, 0 and 15 with a mean of 2.1. The 10.7 cm flux was 70.6, 69.7, 69.4, 69.2, 67.7, 68.8 and 69.5 with a mean of 69.3. The estimated planetary A indices were 3, 5, 4, 5, 4, 2 and 3 with a mean of 3.7. The estimated mid-latitude A indices were 0, 5, 2, 3, 3, 2 and 3 with a mean of 2.6.
Now that we have all the data for the month of April, it is time to present our running 3-month average of daily sunspot numbers, centered on March. The last time we presented this was four weeks back, on April 3. We were hoping last fall that the sunspot minimum was centered around August 2008, when we showed the 3-month average centered on that month with data from July through September at 1.1. The following two averages for September and October were 2.5 and 4.5, but then it began another decline, to 4.4, 3.7, 2.3 and 2.1 for November 2008-February 2009.
The average daily sunspot number centered on March was just 1.5, so the decline continues. Why so low? From February 1-April 30, we had very few days with sunspots, in fact only 11. There was never more than one sunspot visible on each of those 11 days, and the highest sunspot number (an index which does not equal the number of sunspots) was just 15, and that was this last Wednesday. That is not a high sunspot number, but we haven't had one that high since November 13, 2008 when the sunspot number was 16.
The only days with visible sunspots over the past three months were February 11-14 and 24-26, March 6-7 and April 21, 29 and 30. That's it. And if you add all those sunspot numbers together on those dates, you get a sum of only 133. Divide 133 by the 89 days over those three months, and you get an approximation of 1.49438, or 1.5 to round it up.
Here are the latest 3-month averages of daily sunspot numbers:
Jan 07 22.7
Feb 07 18.5
Mar 07 11.2
Apr 07 12.2
May 07 15.8
Jun 07 18.7
Jul 07 15.4
Aug 07 10.2
Sep 07 5.4
Oct 07 3.0
Nov 07 6.9
Dec 07 8.1
Jan 08 8.5
Feb 08 8.4
Mar 08 8.4
Apr 08 8.9
May 08 5.0
Jun 08 3.7
Jul 08 2.0
Aug 08 1.1
Sep 08 2.5
Oct 08 4.5
Nov 08 4.4
Dec 08 3.7
Jan 09 2.3
Feb 09 2.1
Mar 09 1.5
So if we examine the 3-month averages since January 2007, we see what we thought was a minimum of 3.0 centered on October 2007, then another decline to 1.1 in August 2008, and now after rising slightly it has dropped again, to 1.5. And of course we have no way of knowing if next month the number will be lower or higher.
If you look at the sunspot numbers for the three days with sunspots in April -- April 21, 29 and 30 -- the numbers 11, 15 and 12 only add up to 38. Divide that by April's 30 days, and the average is about 1.267, less than the 3-month average ending yesterday. So if we saw the same activity (or lack of it, actually) for May, we could see another decline at the beginning of June when we look at the averages centered on April. If by chance we have no sunspots at all through the end of May, that average would decline from approximately 1.494 centered on March, to 0.681 centered on April.
Last week's bulletin mentioned the Weak Signal Propagation Reporter Network. This week we heard from David Witkowski, W6DTW, of San Jose, California, who said that WSPR was developed by Joe Taylor, K1JT, the 1993 Nobel Laureate in Physics who brought us WSJT and JT65. David recommends going here for getting set up. Also note the link selections on the left side of that page for info on WSJT and JT65. WSJT is a mode for communicating via brief meteor scatter propagation, and JT65 is useful for moonbounce and troposcatter modes.
Last week's mention of the first signs of early 2009 e-skip season brought a response from Jon Jones, N0JK, who says most of the openings have been short, and best for those in Arizona, Texas, Florida and Central America. At the start of the season, conditions are better for the southern tier, but later e-layer openings improve further north. He sent a log of 6 meter contacts on April 22, from 2158-2206 UTC on 50.125 MHz. N0JK (EM17) worked K9NU (EN44), VA2JOT (FN45ER) worked KI4FCQ (EM72NK) and UT1FG/MM worked K1TTT.
Last night (April 30), Rob Geursten, N1KEZ, of Beaverton, Oregon, worked some unexpected DX on 20 meter PSK31 at 0545 UTC. He copied a Bulgarian special event station, LZ2009KM, working many European Russians, and Rob worked Wolfgang, DL2MWB, in Memmingen, Germany. He was surprised to find 20 meters open at this time of day. The sunspot number was 12 -- and 15 the day prior -- but a check with the W6ELprop software shows that with or without sunspots, communication over that path on the first of May is not surprising at that time of day, 10:45 PM at Rob's end. I ran the numbers a month ago and the path wasn't there, but for this late in the spring, communication becomes more likely. Don't miss this excellent tutorial for using W6ELprop, written by Carl Luetzelschwab, K9LA.
Bob Rumsey, KZ5R, of Denton, Texas, wrote in comparing current conditions to 45 years ago during the minimum following Solar Cycle 19: "I would like to add a different perspective to the current solar minimum. Licensed originally at age 14 in 1962, I worked the HF bands diligently until I left for college in 1966. Unless I am mistaken, this was also a period of very low sunspot activity (there was little understanding of it then) and as a General class on 50 W of AM and using a 40 meter dipole and 2 element triband Yagi, I worked little to no DX. I remember an opening during a contest in 1965 when I worked G3CAZ and thought I had walked on the moon.
"From 1966 to 2006, I kept my license active, but other than a stint with VHF in the 1970s, I did little hamming. Then after retiring early and starting my own business, I once again had some time and felt the tug of the HF bands. I built up my station and was amazed at what the technology can now accomplish. Working either coast of the US is a day-to-day occurrence, and Europe or Asia are quite frequent. So you can imagine my surprise when I began reading how we were once again in a solar activity downturn while I'm thinking, 'Wow, this is great!'
"From November 2006 when I put up my vertical disguised as flagpole, I have worked 106 countries running from 100-1000 W. To me, this is heaven, and of course in 2006, conditions to me where what I remembered as normal. The vertical is my primary antenna since I live in a restrictive CC&R community. So as you might have guessed, because of the current technology, I am actually quite happy with the current conditions and cannot wait to see what true solar activity will bring. The proverbial 'kid in a candy store' comes to mind. Thanks for letting me provide an alternative viewpoint on today's conditions."
Thanks Bob. Readers can check out Bob's bio here.
I started in ham radio a few years after Bob -- in 1965 -- and one big difference is that back then I had a very poor receiver; most of my attempts at antennas didn't work very well. To look at the sunspot minimum back then, use this tool that shows that the minimum between Solar Cycles 19-20 was probably around the middle of July 1964.
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.