Propagation de K7RA

More zero sunspot days are finishing out the month, which seems appropriate as we descend near the bottom of Solar Cycle 23.

There were seven continuous spotless days from December 18-24, then three days of sunspot numbers 31, 25 and 23, and Thursday, December 28 was another zero sunspot day. Solar flux numbers, which are not a count of sunspots, but instead a reading of daily 2.8 GHz energy from the sun, still seem high for the bottom of the cycle.

We should see extended periods with a daily solar flux around 67 toward the bottom of the sunspot cycle. Instead, this week the average solar flux was around 74. If we look back to the four bulletins published a decade ago in October 1996, we see average solar flux of 69.9, 68.6, 67.9, and 69.7.

This is the last bulletin of 2006. Next week we will have all the data to observe the average sunspot numbers for the year, and compare them with previous years. With just a few more days left in 2006, it looks like annual average daily sunspot numbers will be running nearly 23 points lower than 2005, which is down 46 percent, and the annual average of daily solar flux will be around 12 points, or 13 percent lower.

For the last days of 2006 into New Year's Day we should see quiet conditions, and no geomagnetic storms or days with active conditions are expected until January 2-3, with a predicted planetary A index of 25. Geophysical Institute Prague predicts quiet conditions for December 29-31, quiet to unsettled January 1, active conditions January 2, unsettled to active January 3, and unsettled January 4.

Solar flux is expected to rise daily through the week, with
predicted values for December 29 through January 4 of 75, 80, 85, 90, 95, 100 and 100. Sunspot numbers should also rise over the next week.

Expect good conditions for Straight Key Night, the annual casual operating activity running from 0000z through 2400z on January 1, which of course covers all of New Year's Eve here in North America.
For details, see http://www.arrl.org/?artid=7050 and the rules for this popular activity at,
http://www.arrl.org/contests/rules/2007/skn.html.

On the Saturday before Straight Key Night (actually tomorrow, December 30) AM operators using primarily big tube type equipment will have their own operating activity, the Heavy Metal Rally, on 160, 80 and 40 meters. See http://tinyurl.com/y2g9qe for details, and for an interesting article from a few years ago see, http://tinyurl.com/gt5d.

Predictions for the magnitude of solar cycle 24, which should begin in 2007 and peak around five years from now, seem to vary all over the place. Some predict one of the strongest most intense cycles in history, while others see a very weak cycle. An article in Space News (a print publication) reported this on December 18, and Doc Silvern, K6RXU of Clarkdale, Arizona passed it on to us. The Space News web site is http://www.space.com/spacenews/, but the full text of the article cannot be seen online.

If you would like to make a comment or have a tip for our readers, email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL Technical Information Service at,
http://www.arrl.org/tis/info/propagation.html.

For a detailed explanation of the numbers used in this bulletin see, http://www.arrl.org/tis/info/k9la-prop.html.

An archive of past propagation bulletins is at, http://www.arrl.org/w1aw/prop/.

Monthly propagation charts between four USA regions and twelve overseas locations are at, http://www.arrl.org/qst/propcharts/.

Sunspot numbers for December 21 through 27 were 0, 0, 0, 0, 31, 25 and 23 with a mean of 11.3. 10.7 cm flux was 72.3, 73.2, 72.7, 73.5, 76.4, 75, and 73.3, with a mean of 73.8. Estimated planetary A indices were 14, 14, 15, 10, 6, 3 and 2 with a mean of 9.1. Estimated mid-latitude A indices were 9, 10, 10, 7, 4, 3 and 2, with a mean of 6.4.

Source: The American Radio Relay League

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