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The K7RA Solar Update


The average daily sunspot numbers for the past week dropped less than a point -- from 42 to 41.6 -- compared to the previous week, while the average daily solar flux was down more than 5 points to 86.2. Sunspot numbers for June 30-July 6 were 34, 51, 54, 42, 44, 30 and 36, with a mean of 41.6. The 10.7 cm flux was 89.2, 87.6, 85.6, 86.2, 85, 84.8 and 84.6, with a mean of 86.1. The estimated planetary A indices were 6, 13, 6, 8, 11, 14 and 8, with a mean of 9.4. The estimated mid-latitude A indices were 3, 7, 3, 6, 7, 8 and 7, with a mean of 5.9.

Predicted solar flux for the near term is lower than of late, with values at 88 for July 8, 90 on July 9-11, 92 on July 12-13, 94 on July 14, 90 on July 15-17, 88 on July 18-21 and 86 on July 22-29. The predicted planetary A index for July 8-13 is 7, 10, 5, 5, 7 and 7, followed by 5 on July 14-18. This is followed by a rise in geomagnetic activity on July 19-24, with planetary A index at 7, 8, 12, 15, 10 and 7. Geophysical Institute Prague predicts unsettled activity on July 8, quiet July 9, unsettled July 10-11, quiet to unsettled July 12 and quiet July 13-14.

The latest smoothed sunspot number prediction on page 13 shows the numbers for December 2010-December 2011 slightly lower. Last month’s prediction showed smoothed sunspot numbers for that period at 30, 34, 38, 41, 45, 49, 54, 59, 63, 66, 68, 71 and 74. The latest has the values for those same months changed to 29, 32, 36, 39, 43, 47, 52, 57, 61, 64, 66, 69 and 72. The reason that in July we see last December’s number change is because the smoothed sunspot number represents an average of data over one year. The data for approximately six months after December 2010 wasn’t completely known until the end of June, and each successive month after that contains one more month of predicted data, instead of data that is actually measured.

NASA has a new monthly solar cycle prediction. Because these are not archived and the URL never changes, tracking the updates can be a bit daunting, but here are the changes from a month ago.

In paragraph 9, this sentence: “We find a starting time of May 2008 with minimum occurring in December 2008 and maximum of about 59 in June/July of 2013” in last month’s prediction has been changed to “We find a starting time of October 2008 with minimum occurring in December 2008 and maximum of about 69 in June/July of 2013.” So NASA now believes the solar cycle started five months later than previously reported, and that the smoothed sunspot peak will be 10 points, or 17 percent higher. These are international sunspot numbers, not the Boulder numbers used in this bulletin (which are higher).

Also changed at the end of that same paragraph, from last month’s prediction: “At this phase of Solar Cycle 24, we now give 40 percent weight to the curve-fitting technique of Hathaway, Wilson and Reichmann Solar Physics  151, 177 (1994). That technique currently gives highly uncertain (but smaller) values to Ohl’s method” to “At this phase of Solar Cycle 24, we now give 50 percent weight to the curve-fitting technique of Hathaway, Wilson and Reichmann Solar Physics 151, 177 (1994). That technique currently gives somewhat uncertain (but similar) values to Ohl’s method.” So 40 percent was changed to 50 percent, and “smaller” was changed to “similar.”

Joe Molon, KA1PPV, of Stamford, Connecticut, likes to play around with lower power on digital modes. He was running 1.5 W with PSK-31 at 0101 on July 1 when he worked Ukrainian station UX7MX on 20 meters. I think he must use a simple wire antenna, because when I look at an image of his QTH using the hi-resolution images on Bing Maps, I don’t see a tower and Yagi. Or perhaps he uses a vertical. Later that same evening, he logged stations in Belarus and France. Click here to see some nice photos of UX7MX.

In the July 2011 issue of CQ, Tomas Hood, NW7US, for his monthly Propagation column has this headline: “Don’t Believe the Pessimistic Forecasts!” complete with exclamation point. He points out that predictions have been all over the place and are revised frequently. He also notes that some might be tempted to just turn off the radio because of forecasts, but this is self-defeating, because if stations aren’t listening and transmitting, then there is nothing to work. I would also note that while marvelous new tools for solar observation exist now that even a decade ago we didn’t have, there just hasn’t been enough data (only 23 sunspot cycles so far) to make predictions with complete reliability. Maybe after another millennia!

Check out Tomas’ website for similar info to material in his column about the importance of x-rays in enhancing ionospheric propagation. Just scroll down a little way to “More about Background X-rays.”

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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