Register Account

Login Help


The K7RA Solar Update


This lack of sunspots is bothersome. Thursday -- May 13 -- is the fifth day in a row with no spots, and there is no sign of any change. The solar flux has been declining and is now below 70. The predicted solar flux for May 14-19 is 70, then 74 on May 20, 75 on May 21-22, 76 May 23, 78 May 24-25 and 80 for May 26-31. Higher solar flux tends to correlate with more sunspot activity. The same forecast -- actually from NOAA and USAF -- calls for planetary A index of 7 for May 14, 12 for May 15-16, 8 on May 17, 5 on May 18-19 and 13 on May 20. Geophysical Institute Prague predicts quiet to unsettled conditions May 14, unsettled May 15, quiet to unsettled May 16, quiet May 17-19 and unsettled May 20.


Prior to all this quiet, we saw nine new sunspot groups emerge April 28-May 8, with high daily sunspot numbers of 70 and 77 for May 4-5. You can see the sunspot numbers for the first three months of 2010 at here and here for the indices since April 1. Sunspot numbers for May 6-12 were 45, 24, 23, 0, 0, 0 and 0, with a mean of 13.1. The 10.7 cm flux was 79.1, 79, 78.8, 75.4, 73.6, 73.5 and 71.2, with a mean of 75.8. The estimated planetary A indices were 10, 9, 6, 4, 5, 8 and 5, with a mean of 6.7. The estimated mid-latitude A indices were 6, 10, 4, 1, 4, 6 and 4, with a mean of 5.


Luke Steele, VK3HJ, sent a report from Australia on May 13, where fall began as spring started in the northern hemisphere and winter begins in late June. Luke’s grid locator is QF22it and he is in Southeast Australia in Victoria. Luke writes, “Just when we were enjoying improving propagation, conditions have subsided again. Until about a month ago, all bands were working reasonably well, but with the onset of winter, all seems to have gone quiet. Tonight, I had to abandon an 80 meter club net, as I couldn't copy stations 50 miles away. A VK5 station called in, reporting VK3s strong there, about 500 miles away. This happened last winter also. DX worked this evening, JD1BMK on 20 meters CW -- about 569 here -- and a special event station HL30GDM in Korea on 40 meters, about 579. With a spotless Sun, and not much happening on air, I will finally get onto some repairs to the boat anchors, construction of my High Performance Software Defined Radio kit, work on my 160 meter vertical antenna and catch up on my QSLing!”


Luke is experiencing that 80 meter condition in which the maximum usable frequency beaming straight up is not high enough to support regional communications. You can see it in the foF2 readings for Australian ionosondes at Canberra, Darwin and Brisbane.


The foF2 reading is taken by beaming a radio signal straight up as it is swept through the HF radio spectrum and measuring the highest frequency that reflects back. Because local and regional 80 meter coverage depends on this high angle radiation, the foF2 number is a good indicator of the viability of regional coverage. Go here to find data for those same locations back through February and many other locations as well.


Check out Luke’s page and click on his photo for a closer look. Note that recently Luke has worked as a farrier. K5DHY has an image of a recent QSL from Luke here.


Bob Elek, W3HKK, in Central Ohio had some excitement on 6 meters recently. On May 8, Bob wrote, “The sudden rise in sunspots and high K levels of May 3-4 caused a previously dead band to explode with signals from the Gulf Coast of Florida, Georgia, South Carolina and even Texas, Puerto Rico and the Bahamas. Dozens of signals peaked 59+ on my 40 meter ground plane antenna. Stunned by what I was missing, I rushed out and bought a 5 el 6 meter Yagi, assembled it onto a 6 foot high mast strapped to my propane grill on the back deck and turned by the Armstrong method. Alas, the band has been quiet ever since, even for tonight’s 50 MHz Sprint. But I'll be prepared for the next opening! The season is nearing for sporadic E, I am told.”


Scott Craig, WA4TTK, has an updated data file for his solar data plotting utility. Download it here and you can display solar flux and sunspot numbers back to January 1, 1989. In subsequent weeks, you can update the data by copying the latest propagation bulletin here and pasting it into a plain text file then reading the file with Scott’s program to automatically insert the data into the database. If you are using Windows, you would highlight the bulletin text, hit CTRL-C to copy and then open Windows Notepad and past using CTRL-V.



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 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 at






Instragram     Facebook     Twitter     YouTube     LinkedIn