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The K7RA Solar Update


This was another quiet week; the geomagnetic indicators hovered around zero and there were no sunspots. Look at the A values for mid-latitude, high latitude and global here. There was another unusually quiet period this week on Sunday, Monday and Tuesday (, similar to November 11, November 14, and November 18-24. Sunspot numbers for November 27-December 3 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0. The 10.7 cm flux was 68.2, 67, 68.2, 68.4, 68.1, 68.9 and 69.2 with a mean of 68.3. The estimated planetary A indices were 7, 4, 2, 1, 0, 0 and 4 with a mean of 2.6. The estimated mid-latitude A indices were 5, 3, 2, 1, 0, 0 and 4 with a mean of 2.1. Right now on Friday morning, there are one or two sunspots trying to break through. The magnetic activity at our Sun's surface in this area is not quite at a level to indicate a visible spot.

The A index -- a linear value -- is calculated from the eight K index readings for the day; these are logarithmic values. It is somewhat similar to calculating decibels from voltage readings across a known load, only in reverse. For an expanded view, check out these values for the calendar quarter, going back to October 1. Note that big changes in the daily A index reflect relatively small changes in the K index. The K index is calculated from magnetometer readings. Middle latitude is from Fredericksburg, Virginia, and the high latitude numbers are from a magnetometer near Fairbanks, Alaska. The estimated planetary numbers are calculated using data from a number of magnetometers at various latitudes.

Compare forecasts from USAF/NOAA from December 3 and 4. The December 3 prediction shows solar flux at 69 for December 5-7, and 70 for December 8-10. Earlier forecasts had a flux of 70 for only December 8-9, but now on Thursday's forecast (December 4), we see the flux value of 70 extended to a whole week, December 5-11. The change to a predicted solar flux of 70 may coincide with emerging sunspots.

The daily forecast is posted usually after 2100 UTC. But the December 4 forecast has a second set of values, updated at 1149 UTC on December 5. It shows a higher A index prediction (changed from 12 to 15) for December 5. You can often see a day's forecast a little earlier by changing the URL on the latest one. At the end of the URL (Web address) for December 3 are the characters 120345DF.txt, and it changes to 120445DF.txt for December 4. Some time prior to 2100 UTC on December 5, you may be able to see the latest forecast by changing that URL ending to 120545DF.txt, and hitting enter (or F5) to refresh, before the link appears on the main page.

Expect higher geomagnetic activity today (December 5) due to a solar wind stream. On December 4, the high latitude A index rose to 20. As mentioned above, the predicted planetary A index for December 5 is 15.

A note from WE0H, Mike Reid, of Saint Francis, Minnesota, mentions great low-frequency propagation (way below 160 meters) coinciding with the quiet geomagnetic indicators. Mike operates on 600 meters (500 KHz, just below the bottom of the North American AM radio band) with an experimental license, WD2XSH/16. He reported on December 2 that he "worked a 600 meter station in Southern Mississippi at 0700 UTC this morning from Minnesota, with armchair CW copy on both ends. Only running 90 W output here. Very light fading and zero background noise. 600 meters has been real good for a couple weeks or so now. I read this morning on the QRP-L QTH reflector that the HF bands are completely dead, even 160 meters. Strange when the HF bands go dead that 600 meters opens wide open. 1750 and 2200 meters are also in excellent shape. 600 and 2200 meter Part 5 stations have been crossing into Europe the past few nights with real strong signals." You can see a picture of the base of Mike's 600 meter antenna on his Web site; if you click through, you can eventually get to his page about his LF activity.

Last week's Solar Update mentioned Tree, N6TR, and his suggestions for a 160 meter antenna. Regarding the capacitor, he commented, "You can use a piece of coax as the capacitor when you determine you have something that will work. Cut it long and trim it. For high power, you might need to treat the end so it doesn't arc. I spread out the shield and stick the center conductor inside a ceramic insulator."

We received quite a bit of mail in the past week that we can't cover in this edition of the Solar Update, and we hope to get to this later. This includes notes from N8II about good conditions on 160 meters with day-to-day variations, N0JK about 6 meter openings (including thoughts on meteor showers instead of sporadic-E being the predominate mode at times) and WB4SLM on 30 meter mid-day openings to Europe.

Don't forget the ARRL 160 Meter Contest this weekend. Next weekend is the ARRL 10 Meter Contest.

And finally, Sid Sosin, W7SID, of Bellevue, Washington writes, "I have figured out the reason why there has been such a paucity of sunspots for such a long time: It's due to my propensity for terrible timing. Besides getting into stocks at their highs, I also got back into ham radio in 2007 after 25 years off the air, just in time for the low point of the sunspot cycle, and, at age 84, my opportunities for propagation maxima are limited. Unfortunately, my punishment for abandoning hamming for so long is also being inflicted on others."

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 in The ARRL Letter. 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.



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