The K7RA Solar Update
The average daily sunspot numbers were up this week by a tiny bit, from 88.1 to 90.6, while the average daily solar flux was down slightly, from 136.2 to 134.9. Sunspot numbers for January 5-11 were 99, 118, 110, 90, 90, 63 and 64, with a mean of 90.6. The 10.7 cm flux was 141.3, 135.5, 140.5, 135.8, 142.3, 128.8 and 120.1, with a mean of 134.9. The estimated planetary A indices were 5, 5, 5, 4, 6, 4 and 5, with a mean of 4.9. The estimated mid-latitude A indices were 6, 6, 5, 5, 7, 5 and 5, with a mean of 5.6.
I’m looking at recent sunspot data since May 2011 using the WA4TTK Solar Data Plotter. The activity had a rising trend throughout 2011 and seemed to peak around mid-November, but since then has softened.
The latest daily projection from NOAA/USAF shows solar flux about 20 points lower than the average for the week, at 115 on January 13-15, 120 on January 16-20, and then a jump of 25 points to 145 on January 21-26. It declines again to a minimum of 135 on January 3-February 6, but then rises to a peak of 165 on February 17-21. The predicted planetary A index is 5 on January 12, 8 on January 13-14, 5 on January 15-17, 8 on January 18-19, and then back to 5 on January 20-27.
Rulon Passey, W7QR, of Ogden, Utah, pointed out that the solar flux and Ap index forecast were missing from last week’s bulletin. But you can get the same data, updated daily, here.
It is a shame that archives of these forecasts going way back aren’t available. They are up for less than three weeks, or at least the current ones are. But let’s try something interesting: The predicted solar flux of 165 for February 17-21 is rather extraordinary. This is a period of five days, and happens to be right in the middle of what will be our data reporting period for bulletin number 8 on February 24, February 16-22. If we are to take this forecast literally, with a solar flux value of 160 predicted on both the first and last days, on that would be an average solar flux value for that seven days of 163.6.
I was surprised when I searched for the last time our bulletin reported an average at this level or higher. The last time was on November 11, 2011 with data from November 3-9. The average solar flux was 173.7, and average sunspot number was 153.4. But even more surprising was that when I searched for any previous bulletin that reported an average this high or higher, I found that way back on January 17, 2003 -- nearly nine years ago -- we reported an average solar flux of 173.6 and sunspot number of 200.9. This was right before Solar Cycle 23 plunged toward the long quiet period that we recently recovered from with the upswing of Solar Cycle 24.
So let’s track this and see if the prediction for the period six weeks from now changes, by how much and when. I suppose this prediction may be based on a return to norm, assuming that Solar Cycle 24 peaks in 2013, with the fact that the recent activity for the past few weeks has been lower than it was in the last months of 2011.
The current issue of Atlantic Magazine has an entertaining and informative article about the Sun and space weather prediction.
Last week, we mentioned adjustments to the geomagnetic indices. Michael Husler of NOAA sent a link to a page describing the new geomagnetic products, and you can see it here.
Unfortunately, due to a staff retirement in Prague, we are no longer getting the updates from Geophysical Institute Prague. These were begun 34 years ago in January, 1978.
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.