The K7RA Solar Update


The average daily sunspot numbers this week were up more than 47 points to 99.3, while the average daily solar flux rose nearly 35 points to 131.7. Sunspot numbers for July 26-August 1 were 77, 91, 108, 79, 106, 116 and 118, with a mean of 99.3. The 10.7 cm flux was 114.7, 123.3, 126.6, 131.4, 136, 139.8 and 150.1, with a mean of 131.7. The estimated planetary A indices were 4, 5, 11, 6, 13, 6 and 6, with a mean of 7.3. The estimated mid-latitude A indices were 3, 5, 11, 6, 11, 5 and 7 with a mean of 6.9.

Solar flux jumped from 139.8 on Tuesday, July 31 to 150.1 on Wednesday, August 1. The predicted solar flux is 135 on August 3-4, 130 on August 5-6, 125 on August 7-9, 130 on August 10-11, and back down to 120 on August 12-13. The solar flux is expected to drop below 100 on August 16-21. The predicted planetary A index is 8 on August 3, 5 on August 4-19, 8 on August 20-21, 5 on August 22-23, then 8, 8, 12 and 8 on August 24-27.

At the beginning of August, we have some new sunspot data from our three-month moving average. The three-month moving averages centered on January-June 2012 are 83.3, 73.7, 71.2, 87.3, 91.5 and 96.5. The average centered on June 2012 is every daily sunspot number from May 1-July 31 added together, then divided by the number of days, which is 92. You could say that this latest number is the three-month trailing average, or the three-month average centered on June. Every month we include a new month of data, and drop off an old month.

F.K. Janda, OK1HH, says to expect mostly quiet geomagnetic conditions on August 3-4, active-to-disturbed on August 5, quiet-to-unsettled August 6-7, mostly quiet August 8, quiet on August 9, active-to-disturbed again on August 10-11, quiet-to-active August 12-13, mostly quiet on August 14-15, and quiet-to-active on August 16-17.

On the NASA Solar Cycle Prediction page, the only thing that has changed over the past few months is the date. This is issued monthly here.

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.