The K7RA Solar Update


Solar activity dropped this week, with the average daily sunspot numbers declining more than 39 points to 94.7. It’s been 13 weeks since the average daily sunspot number for the week was that low or lower, when we reported an average of 91.7 in the September 16 edition of the Solar Update. The daily sunspot number has been lower than this week’s average, starting December 12 when it was 70, and has since been 77, 65 and 44 through December 15.

No new sunspots emerged on December 9-12, but then sunspot group 1376 appeared on December 13 and 1377 came on December 14. Sunspot numbers for December 8-14 were 142, 116, 90, 103, 70, 77 and 65, with a mean of 94.7. The 10.7 cm flux was 144.8, 143.5, 140, 134.3, 131.5, 133.1 and 132, with a mean of 137. The estimated planetary A indices were 1, 1, 6, 4, 3, 3 and 1, with a mean of 2.7. The estimated mid-latitude A indices were 2, 3, 6, 5, 4, 5 and 2, with a mean of 3.9.

The latest USAF/NOAA forecast has the solar flux for December 16-19 at 124, then 122 on December 20 and 120 on December 21-23. Then it jumps to 150 on December 24-26, 140 on December 27-28 and 145 on December 29-January 4. It then rises to a maximum of 160 on January 8-14, 2012. The predicted planetary A index is 5 on December 16-25, 8 on December 26-29, 5 on December 30 through January 4, 2012, 8 on January 5-6, and then 5 on January 7-21. Geophysical Institute Prague predicts quiet conditions December 16-18, quiet to unsettled December 19, unsettled December 20 and quiet December 21-22.

Ed McKie, KB5GT, of Yazoo City, Mississippi, wrote in about a tool for looking at past solar activity by just entering a date. Ed notes that it hasn’t been updated with new data as of a couple of years back. No word from the webmaster, but perhaps it wasn’t meant to be updated, only providing looks at past sunspot activity prior to the date it was created.

Propagation reports for the ARRL 10 Meter Contest last weekend were positive. Randy Crews, W7TJ, of Spokane, Washington, commented: “Conditions during the ARRL 10 Meter Contest were great as expected with the higher solar flux. Personally, I feel 10 meter propagation has not been this good for the contest since 2002.” He noted that for 2002 and 2003, the solar flux in early December was approximately 150 and 102. For 2010 and 2011, it was 87 and 140. “What a great change!” Randy noted. “Listening to the QSOs, it was like we all had a new horse to ride.”

Rick Cincotta, KI4FW, of Arlington, Virginia, noted some curious short skip propagation last weekend: “During the ARRL 10 Meter Contest on the East Coast in the morning and early afternoon (both days), when the band was opened to Europe and the US West Coast (S9+), I could hear stations, very weakly, calling from locations nearby, closer than the usual E-S ‘doughnut’ that I’m familiar with from 6 meters (these guys were from Eastern Ohio, Southern New York and northern New Jersey, Rhode Island, Connecticut and North Carolina). They never got louder than S1, but I could make out their call signs if I cleaned the wax out of my ears and held my breath -- so to speak. I’m QRP, so I was only able to work a couple of them in New York.”

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.