11 December 2011
The K7RA Solar Update
What happened to that new “grand minima”? Solar Cycle 24 just keeps rolling along -- for the first seven days in December, there were eight new sunspot groups. December 5 had the largest sunspot coverage over the past week, with a daily sunspot number of 185. The average daily sunspot number for the week rose more than nine points to 133.9, while the average daily solar flux values rose exactly 19 points to 156.5.
Sunspot numbers for December 1-7 were 89, 106, 138, 154, 185, 143 and 122, with a mean of 133.9. The 10.7 cm flux was 152.2, 157.3, 164.1, 163.6, 158.1, 151.1 and 148.9, with a mean of 156.5. The estimated planetary A indices were 7, 4, 9, 4, 2, 1 and 1, with a mean of 4. The estimated mid-latitude A indices were 7, 4, 7, 4, 4, 0 and 1, with a mean of 3.9.
NW7US has a graph comparing Solar Cycle 24’s progress with the upswing of Solar Cycle 23. It is based on the RI -- or monthly mean Brussels International Sunspot number -- which is lower than the SWPC Space Weather Operations sunspot numbers that we use in our bulletin. This doesn’t reflect the upswing since the start of each cycle, nor does not show the long quiet period at the start of the current cycle. It just shows the monthly mean data over the 25 months ending in September 2011, compared to the 25 months ending in June 1998.
The latest forecast from USAF/NOAA has the solar flux at 145 on December 9-12, 140 on December 13-16, 160 on December 17-18, and 155 on December 19-22. The planetary A index for the same dates is expected to be 5 on December 9-10, 8 on December 11, and 5 on December 12-22. The solar flux values in the above forecast changed quite a bit from what was reported in the December 8 edition of The ARRL Letter. That was based this forecast, and that forecast is based on this one. Geophysical Institute Prague sees a quiet week ahead, with quiet conditions December 9-11, quiet to unsettled December 12 and quiet again on December 13-15. Conditions should be good for the ARRL 10 Meter Contest this weekend.
Each month new month brings a slight upward revision in the smoothed sunspot forecast. Note the differences between the table on page 19 and the one on page 17.
Click here for an article from the Royal Observatory of Belgium concerning rising solar activity.
Brian Machesney, K1LI, of Craftsbury Common, Vermont, reported some interesting multipath echoes on December 5: “Strong 17 meter CW signals from A71EM to FN34 are suffering from what sounds like multipath echoes at 1330 UTC on December 5. There seem to be at least three distinct paths of nearly equal strength.”
Jon Jones, N0JK, of Wichita, Kansas, sent comments about the winter sporadic-E season: “The winter E-s season is underway. On December 3, KB3RHR in grid square EN90 was into Kansas on 50 MHz at 2315 UTC. This was E-skip. The winter E-s season tends to peak around Christmas. This year -- with the higher solar flux -- the E-s can link to F2 and TEP openings.”
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.