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The K7RA Solar Update

11/04/2011

First, a few updates on Solar Cycle 24. As you might suspect, the average of daily sunspot numbers for October shot way up -- from 55.5 in June, to 67.2 in July, 66 in August, 106.4 in September and 123.6 in October. Our three month moving average of daily sunspot numbers was also up, of course, with the three month average ending in October at 98.6, up from 61.5 in July, 63 at the end of August, and 70.6 ending in September. Because of increasing solar activity, NASA revised its prediction for the peak of the current solar cycle for the third consecutive month, each time estimating higher intensity and changing the projection for the month the cycle is expected to peak.

Note that these numbers are not the higher Boulder sunspot numbers we report here, but the much lower Zurich numbers. They are also smoothed sunspot numbers, meaning they represent an average taken over a year, with the indicated month in the middle. On September 1, NASA moved the expected peak from June 2013 to May 2013, and the smoothed sunspot number from 69 to 70. At one time, they were predicting a maximum nearly the same as the 1907 maximum of Solar Cycle 19, which was 64.2, but recent predictions are substantially above that value. NASA noted that the current cycle would still be the smallest in the past hundred years.

A month later on October 3, they upped it again, with the maximum smoothed sunspot number jumping from 70 to 77 and the peak moving again, this time from May to April 2013. But at this level, it would still be the weakest cycle in 100 years. On November 2, their prediction made a big jump -- from 77 to 89 -- but with the peak moving back out, this time from April to May 2013. This makes the cycle slightly bigger and longer, and instead of 100 years, it is the smallest solar cycle in more than 80 years.

NASA’s prediction for solar max jumped nearly 30 percent in three months -- not bad. Still, a graphic comparing the beginning of Solar Cycle 24 with the last three solar cycles shows how weak it really is. But note this is a 13 month moving average, so the latest point on the graph is over 6 months ago, and the higher activity is recent.

Sunspot numbers for October 27-November 2 were 98, 104, 73, 80, 112, 141 and 121, with a mean of 104.1. The 10.7 cm flux was 131.5, 133.9, 123, 126.7, 138.1, 138.6 and 153.6, with a mean of 135.1. The estimated planetary A indices were 4, 2, 2, 6, 8, 21 and 11, with a mean of 7.7. The estimated mid-latitude A indices were 4, 1, 2, 4, 9, 14 and 7 with a mean of 5.9.

The latest prediction from NOAA and USAF for the near term has solar flux at 165 on November 4-10, 160 on November 11, 150 on November 12-15, 160 on November 16 and peaking again at 165 on November 17-18, then falling to 155, 145, 140 and 130 on November 19-22. For November 4-6, the predicted planetary A index is 15, 10 and 8, then 5 on November 7-10, 12, 10, 8, and 5 on November 8-10, 8 on November 11-13 and 5 again on November 14-23. Geophysical Institute Prague predicts quiet to unsettled conditions November 4, unsettled November 5, quiet to unsettled November 6 and quiet conditions November 7-10.

A huge sunspot group -- number 1339, with an area of 1400 millionths of a solar hemisphere -- has rotated into view. There was one new sunspot group on October 30, three more on October 31, another two on November 1 and another new one on November 2. On Thursday, November 3, sunspot group 1339 was reported to be the biggest sunspot in a number of years. The total sunspot area for that day was 2005 millionths of a solar hemisphere, and a larger total sunspot area has not been observed since July 18-23, 2004 when the total sunspot areas were 2300, 2325, 2190, 2420, 2070 and 2050. It is interesting that no new sunspots appeared during that period, and the daily sunspot numbers were 169, 176, 147, 162, 117 and 86 over those same six days.

The sun is currently peppered with spots, so don’t be surprised if a solar flare is released, possibly disrupting HF radio communications if it is aimed at Earth. MSNBC ran an article on the latest solar activity. You can also watch a video of a flare from sunspot group 1339. Note that you can select twice the default resolution by clicking on the “360p” at the bottom and restarting the video. This gives a very good picture for full screen viewing, accessed by clicking in the lower right of the screen.

Scott Smith, VK2AET, of New South Wales, Australia, wrote to say, “I was enjoying a CW contact with the USA on 10 meters today (November 3) at 2015 UTC when all of a sudden, the band went completely dead. Before this I had just worked EA8, which was quite exciting. After this fadeout, there were no signals at all on 10 meters. It appeared so dead that I thought my antenna had fallen down and I had to look out the window at it. Here in Australia, we get a great indicator of 10 meter propagation by listening to 27.025 MHz, where US CBers are usually well over S9 when the band is in good shape. These guys had also disappeared completely, whereas half an hour before they were their usual strength.”

Scott must have observed an effect from the X-Class solar flare, which peaked about 12 minutes later at 2027 UTC. That is the same flare reported in the article at Universe Today linked above.

The ARRL November CW Sweepstakes is this weekend, and the current solar activity should make 10 meters especially productive.

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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