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The K7RA Solar Update


Solar activity declined again this week, with the average daily sunspot numbers dropping 17.8 points, from 78.9 to 61.1, while the average daily solar flux declined 19.4 points, from 121 to 101.6. Sunspot numbers for November 29-December 5 were 89, 67, 49, 43, 44, 58 and 78, with a mean of 61.1. The 10.7 centimeter flux was 113.1, 110.6, 101.7, 97.7, 96.6, 96.2 and 95.5, with a mean of 101.6. The estimated planetary A indices were 3, 2, 4, 7, 4, 3 and 2, with a mean of 3.6. The estimated mid-latitude A indices were 2, 1, 3, 8, 3, 5 and 4, with a mean of 3.7.

The latest prediction from NOAA/USAF is for solar flux at 95 on December 7, 100 on December 8-9, 105 on December 10, 110 on December 11-12, 115 on December 13-14, 135 on December 15-17, then 130, 125 and 120 on December 18-20, 115 on December 21-23, 110 on December 24-27, 100 on December 28-29, 105 and 115 on December 30-31, 125 on January 1-2, 130 on January 3-7, and rising to 135 on January 8-13. The predicted planetary A index is 8 on December 7-8, 5 on December 9, 8 on December 10, 5 on December 11-14, 8 on December 15, 5 on December 16-28, 8 on December 29-30, 5 on December 31-January 1-6, then 10, 8 and 5 on January 7-9, and rising to 8 on January 10-11.

The above forecast is from Thursday, December 6, and is revised from the one issued a day earlier, which appeared in The ARRL Letter. The latest forecast has lower solar flux over the next few days with slightly more active geomagnetic conditions. We would like to see better conditions than currently forecast for the ARRL 10 Meter Contest this weekend.

Last year on the Friday-Saturday-Sunday of the ARRL 10 Meter Contest weekend (December 9-11, 2011), the solar flux was 143.5, 140 and 134.3, while the planetary A index was 1, 6 and 4. This year prediction for the three days of December 7-9 has a solar flux of 95, 100 and 100, and a planetary A index of 8, 8 and 5. Note that the contest lasts only two days, but we include the day before also, as activity on that date should affect contest conditions. We prefer to see higher solar flux and a lower A index. There is also the possibility of enhanced propagation from ionized meteor trails. The Geminid shower this year peaks on December 13, but the Geminid activity runs from December 4-17, so we may see 10 meter propagation enhanced somewhat by the early part of the shower.

Let’s look at some moving averages for sunspot numbers. We have tracked a three-month moving average for quite some time now. The highest activity in this cycle was during the peak in fall 2011, when the three months centered on October 2011 had an average daily sunspot number of 118.8, and the November 2011 centered average was 118.6. Now that November has ended, we know the three-month moving average for September 1-November 30. The averages for this year centered on January-October were 83.3, 73.7, 71.2, 87.3, 91.5, 96.5, 91.9, 89.9, 81.2 and 82.3. The monthly averages of daily sunspot numbers for August-November were 85.8, 84, 73.8 and 89.3.

Another thing to look at is the yearly average of sunspot numbers, and 2012 doesn’t look bad. The average annual sunspot numbers for 2008-2011 were 4.7, 5.1, 25.5 and 29.9, and the average for 2012 to date (through December 6) was 83.8 -- quite a jump from last year’s 29.9. We got 83.8 by summing all the daily sunspot numbers from January 1-December 6, which was 28,581, and then divided that by the number of days, which is 341.

Ken Miller, K6CTW, sent us the link to the Australian Government Radio and Space Weather Services. We’ve mentioned this site before, but Ken points out some interesting features: “One of their features are HAP charts, which are designed to indicate the best frequency range at that hour for communications between a specified base and mobile within a nominated area.”

To access these, click on “HAP Charts,” located on the left-side menu bar under Global HF. When the “HAP Charts” menu appears, click on “Hourly HAP Charts.” Using the pull-down menu, select the center point nearest to your station. When Ken is home, he uses Phoenix (even though he’s actually in California). Then click on the “Display” button.  According to Ken, the chart is very intuitive and the details of what it is indicating are summarized below the chart.

“Lately, in the evenings, I have seen charts indicating red, which show that the best communications for our traffic nets area would be from 1-3 MHz,” Ken said. “When that is indicated, signals have usually been very degraded or even a total wash-out. The ‘old school’ saying is that the band has gone ‘long.’ These charts have been very accurate and could benefit both NTS and DX operators alike.”

Howard Lester, N7SO, of Schuylerville, New York, wrote this on December 1: “At 2145 today I worked RO9O in Asiatic Russia on 14.021 MHz CW. He was a true 599 (with flutter -- a polar path), and he gave me the same (but of course, who knows, considering my 100 W and dipole antenna). Current conditions have the solar flux at 102 and the K index at 2. The W6EL propagation program, for those conditions, gives a prediction of 32 (signal level) D, D being the ‘1-25 percent probability’ category, and with a fairly low signal at that. The moral of the story is that it pays to listen, or at least check!”

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.




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