The average daily sunspot numbers for this week declined more than 7 points to 27.6 from the previous week, December 2-8. The solar flux was about the same as last week, with the average up less than a point. Sunspot numbers for December 9-15 were 22, 33, 25, 23, 46, 33 and 11, with a mean of 27.6. The 10.7 cm flux was 86.8, 88.4, 86.9, 89.4, 87.7, 90.3 and 86.9, with a mean of 88.1. The estimated planetary A indices were 2, 0, 1, 4, 5, 11 and 9, with a mean of 4.6. The estimated mid-latitude A indices were 0, 0, 1, 3, 5, 10 and 8, with a mean of 3.9.

The predicted planetary A index for the next 10 days -- December 17-26 -- is 5, 8, 8, 5, 5, 8, 5, 5, 7 and 5. Solar flux for the same days is predicted at 82, 80, 80, 78, 78, 78, 78, 78, 88 and 88. Flux values are expected to rise to 90 by December 29 through January 1. Geophysical Institute Prague predicts quiet to unsettled conditions for December 17, unsettled December 18-19, quiet to unsettled December 20 and quiet December 21-23.

A week ago, two sunspot groups were visible, 1131 and 1133. The last day 1131 could be seen was December 14, after which it rotated out of view. It first appeared on December 2 and was a big sunspot group. Comparable sized groups were 1108 on September 16-28, 1109 on September 21-October 4 and 1117 on October 19-November 1. All other recent groups have been much smaller. Sunspot group 1133 is rotating out of view, visible for 13 days after arrival on December 4. The Sun would be spotless, but a new sunspot group 1135 emerged on Thursday, December 16 when the daily sunspot number rose from 11 (the minimum non-zero value, on Wednesday) to 23.

John Kountz, WO1S, of Laguna Beach, California (also T6EE when he was in Kabul), sent some info on a new piece of free software from NASA called JHelioviewer for examining images from the Solar Dynamic Observatory (SDO). John and I have both installed this software, but haven’t yet figured out where to get the SDO data. With it, we should be able to examine any images from the SDO project, which was launched on February 11, 2010. For instance, it might be interesting to look at images of sunspot group 1108 by grabbing images of the Sun from September 16-28. There is an online version of the program here. You can enter a date and then choose an interval in the Time-Step field. Setting it to 12 hours and clicking on the arrow to the right of that field gives a nice twice-a-day solar image that shows emergence of activity and tracks it across the earth-facing side of the sun.

Go here to look at quarterly sunspot data and pick a period with high sunspot numbers. For instance, stepping through 12 hour increments beginning on October 16 shows quite a lot of interesting activity. Take the interval down to 15 minute increments, and you can examine a great deal of detail as prominences emerge and decay.

Scott Bidstrup, TI3/W7RI, and several other readers sent references to an article here about a solar event on August 1 and how it was observed by the SDO and STEREO projects. If you go here, you can see the resulting A and K indices several days later. While this was a fairly large event, what made it so interesting this time were all the instruments in place for observing it.

Pete Heins, N6ZE of Thousand Oaks, California is in grid square DM04ne where he operates on 6 meters. He didn’t say if he was using SSB or CW, but on December 14 for about 90 minutes, he worked quite a bit of E-skip. He first heard K0GU (DN70) at 0250 while mobile. No doubt hearing e-skip sent Pete home, where 9 minutes later, he worked W7GNE (DM43), then W0GMO (DN70) at 0306, AB7OI (DN41) at 0413, WA7YAZ (DN40) at 0422 and NJ7A (DN30) at 0437. Arizona, Colorado and Utah. Not bad!

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 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.