The K7RA Solar Update
Both the sunspot numbers and the solar flux barely changed in the past week: The average daily sunspot numbers were 55.7, down slightly from 56.4 the previous week, while the average daily solar flux was 98.7, down from 110.7. Geomagnetic conditions continued their quiet spell. The most active day was Saturday, January 26, when both the mid-latitude and planetary A index were 18, and Alaska’s College A index was 46. Sunspot numbers for January 24-30 were 60, 44, 55, 60, 52, 63 and 56, with a mean of 55.7. The 10.7 centimeter flux was 103.4, 100.5, 99.4, 97.7, 97.6, 95.4 and 96.6, with a mean of 98.7. The estimated planetary A indices were 1, 6, 18, 6, 4, 2 and 2, with a mean of 5.6. The estimated mid-latitude A indices were 1, 7, 18, 5, 3, 2 and 2, with a mean of 5.4.
The predicted solar flux is 100 for February 1, 105 on February 2-5, 110 on February 6-7, 120 and 125 on February 8-9, 120 on February 10-11, then 115, 110 and 105 on February 12-14, 110 on February 15-18, 105 on February 19-23, 95 on February 24-25, 110 on February 26, and rising to 125 on February 27-March 1. Flux values are predicted to peak again at 140 on March 3-4.
The predicted planetary A index is 5 on February 1, then 12, 18, 15 and 8 on February 2-5, 5 on February 6-8, 8 on February 9-10, 5 on February 11-18, 8 on February 19, 5 on February 20-21, then 15, 10 and 8 on February 22-24, 5 on February 25-March 7, and back to 8 on March 8-9.
Regular readers know that we’ve been tracking a three-month moving average of sunspot numbers for several years now. The average daily sunspot number for the three calendar months ending January 31 was 82.8, better than last month, but nothing like the numbers we saw more than a year ago in fall 2011. The three-month averages for the past year -- the months ending in February 2012-January 2013 -- were 83.3, 73.7, 71.2, 87.3, 91.5, 96.5, 91.9, 89.9, 81.2, 82.3, 74.4 and 82.8. The one-month average sunspot number for January was 98.9, the highest monthly average since May and July of last year.
There’s not much news from readers this week, but Jeff Hartley, N8II, of Shepherdstown, West Virginia reported this on January 25: “Today was pretty decent, considering the now-double digit solar flux index and K of 2. I worked RC4HAA on 15 meter CW who was S6-9, and 12 meters opened well to Europe from 1400-1440. I got in on the tail end of it with contacts with Greece, Switzerland, Slovakia and England. Last night at 0200, I caught T6LG in Afghanistan on 80 meter CW for a new band/country. He was about S3-S6 and not hearing the USA stations calling him that well (there were about 10 callers when I was there).”
Glenn Axelrod, N6INM/9, in Mundelein, Illinois, wrote: “Are the solar flux numbers and conditions going to improve by the spring and summer? Are we ever going to see numbers again -- like we saw in 1958 -- in my lifetime?”
We have no way of knowing when this solar cycle will peak, or even if it may have already peaked, but peaks of solar cycles become easier to predict later in the first part (the upswing) of any cycle. Until recently, experts predicted this cycle – Solar Cycle 24 -- would probably peak in spring of 2013, which begins in less than seven weeks. But later predictions moved it out to fall of 2013, with slightly lower numbers. We had a period of higher solar activity in November and December of 2011, leading some to believe that perhaps the cycle had peaked early. Others believe we may see a double-peak in this cycle, as we have in some earlier solar cycles. But we should see seasonal improvements in HF conditions in the spring and again in the fall. By seasonal, I mean that even if we saw no change in solar activity, just due to the season and position of the Sun relative to us, we see better conditions on the higher frequencies in spring and fall than we tend to see in summer and winter.
n September-December 2011, the monthly averages of daily sunspot numbers were 106.4, 123.6, 133.1 and 106.4. The previous four months (May through August) saw averages of 61.5, 55.5, 67.2 and 66, so the final third of 2011 showed a dramatic jump in activity. But the next year, the numbers dropped back again. The average daily sunspot number for all of 2012 was 82.3, while the average for all of 2011 was only 29.9, so that jump at the end of the year was exciting, and convinced many of us that the cycle was starting to really ramp up. The January 2013 average was a little less than 100.
There is a hypothesis which posits that we may see a grand minimum -- decades of depressed sunspot numbers -- but of course, that cannot be proven by observation in the next decade or two. I hope it isn’t true. I hope we see future activity which is strong and surprises everyone, but I wouldn’t count on it. I was licensed during the low point between Solar Cycle 19 (the biggest in history) and Solar Cycle 20, and along with many others, I have been wishing for decades to see another like Solar Cycle 19. But that cycle turned out to be a rarity. But just like Solar Cycle 19 surprised many people, I hope we can be surprised again.
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.