Propagation de K7RA

The IMF, or Interplanetary Magnetic Field, dipped south early
Thursday UTC (Wednesday night, November 29 in North America) letting in a blast of solar wind.

The planetary K index throughout Thursday UTC (which is 4:00 PM Wednesday to 4:00 PM Thursday here on North America's West Coast) was 2, 4, 5, 5, 5, 5, 2 and 1, and the resulting planetary A index was 28. This week saw more geomagnetic activity overall than the last reporting week (it runs Thursday through Wednesday), with the average daily planetary A index rising 8.7 points to 12.3. Average daily sunspot numbers declined more than 11 points this week over last.

The daily sunspot number was 0 on three days recently, November 22-24. Since that time the number has been rising (12, 12, 30, 34, 33 and 59) from November 25-30. There are two prominent and growing sunspots in view (927 and 926) and a holographic image from November 26 shows a mid-sized sunspot on our Sun's far side. Not bad for a low point in solar cycle 23.

Current predictions show the sunspot minimum to be 3-4 months from now, although by then I would expect to see more spotless days, up to several weeks in a row at least.
The predicted minimum is based on predicted monthly smoothed sunspot numbers, so we will see quite a bit of variation, since daily reality is not "smoothed." To determine a true smoothed sunspot number for any month, you need 13 months of daily readings, so currently we could only know an actual smoothed sunspot number as recently as May 2006.

The average daily solar flux for the past week was 80.6, and the latest prediction shows that number rising to 85 for December 1-5, 90 for December 6-7, and 95 during December 8-13. Sunspot numbers should rise also. Over this weekend the planetary A index is expected to quiet down, with a value of 15 for December 1, and 5 for December 2-5. The next period of geomagnetic disturbance is expected around December 7, with a planetary A index of 25. This is just prior to the ARRL 10 Meter Contest, December 9-10. Geophysical Institute Prague predicts quiet to unsettled conditions December 1, quiet conditions December 2-5, unsettled December 6, and active geomagnetic conditions on December 7.

November is over, so we can calculate monthly averages and look at where we are and where we've been.

The average daily sunspot numbers for the months November 2005 through November 2006 were 32.2, 62.6, 26.7, 5.3, 21.3, 55.2, 39.6, 24.4, 22.6, 22.8, 25.2, 14.7 and 31.5. Average daily solar flux for the same months was 86.3, 90.8, 83.4, 76.5, 75.5, 88.9, 80.9, 76.5, 75.8, 79, 77.8, 74.3 and 86.3.

The numbers for November are a surprise, although not outside the range of normal variation.

In Propagation Forecast Bulletin ARLP042 dated October 13, 2006 there was a description of how smoothed sunspot numbers are calculated. From the monthly averages above, we can calculate our own smoothed sunspot number for May 2006. We take half of the November 2005 average and half of the November 2006 average, add them to the monthly averages for the intervening 11 months, and divide by 12. So that is 16.1 plus 15.75, plus the 11 month total of 320.4, which equals 352.25. This shows an unofficial smoothed sunspot number of 29.4 for May, 2006. If we just average the daily sunspot number over those 13 months, that average is 29.75.

Enough numbers, and a little about propagation. After last weekend's CQ Worldwide CW DX Contest, Allan Mason, VK2GR in Sydney, Australia noted that 10 meter trans-equatorial propagation was good over both days between VK2 and Japan with little QSB. He also worked 9M8 and UA9 on 10, but 80 and 40 meters were the best bands to work Europe and North America. Allan used 100 watts and inverted vee antennas.

Ed Clulow, N7TL of Portland, Oregon reports he heard nothing on 10 meters over the weekend, "but 15 was sure inspiring both days." Paul Gray, N0JAA of Satellite Beach, Florida was surprised to work EA8EQ in the Canary Islands on 12 meter SSB around 1700z earlier in the week. Paul was using a G5RV antenna, and EA8AQ was quite strong. Paul believes this was sporadic-E skip.

Herb Anderson, K7GEX of Seattle, Washington wrote to ask about different geomagnetic numbers. He uses the VE7CC packet cluster, and noticed that postings of geomagnetic A and K index by different parties show different results. On November 28 at 0000z, DK0WCY reported A index of 12, and K of 2, but K3SKE reported A of 9 and K of 1. "Why the difference?", Herb asks.

I used telnet to connect via the internet to VE7CC, and noticed that K3SKE must have been reporting data from WWV. That would be the local Boulder A and K index in Colorado. DK0WCY reports at, http://www.dk0wcy.de/
magneto/magnet.htm that he has his own magnetometer, which perhaps is where he was getting the numbers that he reported. Generally magnetometers in higher latitudes report greater geomagnetic disturbances.

For instance, if you look at, http://www.sec.noaa.gov/
ftpdir/indices/DGD.txt you'll see that the numbers in Alaska are generally higher than the numbers from Fredericksburg, Virginia. Boulder, Colorado is around 40 degrees north latitude, while DK0WCY is in the far north of Germany at Scheggerott with a latitude of 54.33 degrees north. Fredericksburg is around 38.3 degrees north, while Herb in Seattle lives at 47.776 degrees north.

The link above also shows planetary A and K index, and these numbers are derived from 13 magnetometers around the world. You can learn more about them at,
http://www.gfz-potsdam.de/pb2/pb23/GeoMag/niemegk/
kp_index/kp_sites.html and http://www.gfz-potsdam.de/
pb2/pb23/GeoMag/niemegk/kp_index/kp.html.

I was watching the local late evening news on television in Seattle, and saw a story about the new Japanese Hinode spacecraft, which carries several high resolution telescopes. The news story showed dramatic footage of solar prominences and sunspots. You can see images from this new satellite at, http://solar-b.nao.ac.jp/news_e/
20061127_press_e/.

Last, Ward Silver, N0AX had a couple of fascinating items in the latest issue of the ARRL Contest Rate sheet this week. One was a story out of India about cooling in the upper ionosphere. Ward commented that cooling in the lower layers should improve density, which of course translates to higher MUF and better propagation at higher frequencies. You can read about it at, http://tinyurl.com/yxoked.

Also in the same issue was a link to a fascinating and useful online tool for propagation prediction which shows the optimum ham band for working anywhere in the world based on CQ DX Zones. It is at, http://www.radiosport.ca/
zoneprop. If you're not sure which zones are where, just click on the CQ DX Zones link on the left.

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 November 23 through 29 were 0, 0, 12, 12, 30, 34 and 33 with a mean of 17.3. 10.7 cm flux was 76.8, 77.4, 78.6, 78.2, 82.4, 85.5, and 85, with a mean of 80.6. Estimated planetary A indices were 18, 21, 15, 15, 6, 5 and 6 with a mean of 12.3. Estimated mid-latitude A indices were 8, 10, 10, 9, 7, 4 and 6, with a mean of 7.7.

Source: The American Radio Relay League