The K7RA Solar Update
The average daily sunspot numbers for the week rose nearly 27 points to 92.4, while the average daily solar flux increased more than 9 points to 98.2. Sunspot numbers for July 14-20 were 79, 90, 75, 101, 127, 96 and 79, with a mean of 92.4. The 10.7 cm flux was 94.1, 93.8, 93.8, 103.6, 102, 100.3 and 100.1, with a mean of 98.2. The estimated planetary A indices were 8, 6, 6, 5, 8, 18 and 19, with a mean of 10. The estimated mid-latitude A indices were 6, 5, 4, 3, 6, 10, and 12 with a mean of 6.6.
The latest prediction has solar flux values for the next week a little lower than those listed in Thursday’s ARRL Letter. Expected values are 96 for today (July 22), then 95 on July 23-27, 98 on July 28, 90 on July 29-August 2, 95 on August 3-7, 98 on August 8, and then back to 100 on August 9-16. The planetary A index for July 22-23 is predicted at 10 and 8, then 5 on July 24-28, 8 on July 29-31, then 10, 8, 5 and 8 on August 1-4, 12 on August 5-7, and back to 8 on August 8-10. Geophysical Institute Prague has a weekly prediction for geomagnetic indices that doesn’t use the A or K index, but instead has seven levels of activity, from quiet to severe storm. Their prediction for this week says to expect unsettled conditions for today (July 22), quiet to unsettled on July 23, quiet July 24-25, quiet to unsettled July 26-27 and quiet again on July 28.
There seems to be plenty of sunspots visible over the past week, but nothing really large or very active. Sunspot areas are counted in millionths of a solar hemisphere, and on Thursday. July 14, there were six sunspot groups visible: 1245, 1250, 1251, 1252, 1254 and 1255. The area ranged from 5 for sunspot group 1245 to 100 each for groups 1250 and 1251. The total sunspot area for that day was 265.
On Friday, July 15, new sunspot group 1256 was added, and the total sunspot area was 260, as the other sunspot groups shrank, except for 1251 and 1254. On July 16, 1255 disappeared and the total sunspot area dropped to 230. On Sunday, July 17, sunspot areas 1245 and 1252 disappeared, new group 1257 was added and the total sunspot area grew to 280. On Monday, July 18, the sunspot area jumped to 400 when two new groups -- 1258 and 1259 -- were added. On July 19, the sunspot area jumped again to 660 when 1255 disappeared and all sunspot groups except 1256 grew. Groups 1250, 1257 and 1258 each doubled in size, while 1259 more than tripled. On July 20, groups 1256 and 1257 disappeared and sunspot area dropped by more than half to 310. On July 21, groups 1250 and 1258 went away and sunspot area declined from 310 to 290; the daily sunspot number declined from 79 to 56.
There has been quite a bit of news about a predicted grand minima in solar activity. We recently reported on a conference where three lines of evidence were presented, seeming to point to a future disappearance of sunspots, perhaps like the dreaded Maunder Minimum. I am not unbiased in this regard, and like most radio amateurs, yearn for high solar activity. Alas, a return of Solar Cycle 19, the granddaddy of them all, seems elusive. But there is some dissent regarding these predictions of no sunspots, which gives us hope.
On Wednesday, I spoke with Dr. Douglas Biesecker, an astrophysicist at the NOAA Space Environment Center in Boulder. He was mentioned in the Solar Update for June 17, dissenting from the assertion that evidence points toward sunspots disappearing or another Maunder Minimum in our future.
He mentioned something called a Gleissberg Cycle. When we do a really long smoothing of sunspot numbers, the smoothed sunspot numbers we are familiar with -- the data used in those nice graphs of sunspot cycles -- average data over 13 months. So every place you look on the graph doesn’t show the variation that occurred during that month, but instead averages data over more than a year, to smooth out all the noise of daily variations. But what would happen if you smoothed the numbers over a much longer period, say 11 years? Could you find some periodicity that would suggest a cycle of cycles or perhaps predict clusters of decades with low or high solar activity?
Gleissberg cycles suggest a periodicity of about 87 years, and some have studied these to try to predict general levels of solar activity over multiple decades. But if a cycle is 87 years long -- and we only have about 256 years of directly observed solar data -- the most we could look at would be less than three cycles. That isn’t enough data to make even crude speculative projections.
Doug mentioned what he referred to as an “old NASA axiom,” that goes something like this: “If you can’t see something happen seven times, it isn’t real.”
Doug said he is attending Solar Heliospheric and Interplanetary Environment (SHINE) workshops. At these meetings, participants have been hashing out the evidence for or against a “no Solar Cycle 25” scenario, and discovering some problems with the three lines of evidence pointing toward a disappearance of sunspots. They haven’t reached a consensus, but he believes that positions may be moving away from predicting another Maunder Minimum. On this topic, take a look at this website.
A new issue of WorldRadio is now available. On page 20, you’ll find the monthly Propagation column by Carl Luetzelschwab, K9LA. This time it is titled “Here’s Some Help to Explain Those Unusual QSOs.” Carl looks at propagation that doesn’t seem to be supported by the MUF or general level of solar activity at the time, and offers some interesting ideas on what might really be going on.
If you are fortunate enough to be in Kansas City this weekend, you can catch Carl’s talk on propagation at W0DXCC-2011 on Saturday, July 23. His talk begins at 9:30 AM in the W0JM Room and is called “Our Recent Sunspot Minimum, and the new Sunspot Cycle 24.”
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.