The K7RA Solar Update


The average daily sunspot numbers sank nearly 50 points this week to 94.3, while the average daily solar flux was down more than 16 points to 117.8. The geomagnetic indices were quite high, due to a solar wind storm. Sunspot numbers for May 23-29 were 117, 99, 107, 92, 87, 75 and 83, with a mean of 94.3. The 10.7 centimeter flux was 134.5, 127.3, 121.3, 120, 110.1, 104.8 and 106.9, with a mean of 117.8. The estimated planetary A indices were 7, 20, 32, 18, 13, 8 and 2, with a mean of 14.3. The estimated mid-latitude A indices were 8, 17, 25, 19, 8, 8 and 2, with a mean of 12.4.

The predicted solar flux for the near term is 105 for May 31-June 1, 110 on June 2-5, then 105, 115, 125 and 130 on June 6-9, 135 on June 10-11, 140 on June 12-13, then 135, 125, 135 and 130 on June 14-17, and falling to 125 on June 18-20. The predicted planetary A index is 18 on May 31, 15 and 10 on June 1-2, 8 on June 3-4, 5 on June 5-10, then 8, 12, and 8 on June 11-13, and back down to 5 for June 14-17.

The Australian Space Forecast Centre issued an alert on May 30 at 0524 UTC, warning of increased geomagnetic activity due to a solar wind stream from a coronal hole. They predict mostly unsettled-to-active conditions on May 31, with the chance of minor storm periods in the latter half of the day at high latitudes. For June 1, the forecast is calling for mostly unsettled conditions with a chance of active periods.

Rich Zwirko, K1HTV, of Amissville, Virginia, wrote on May 29: “I worked my first European of the 2013 6 meter E-skip season at 2200 yesterday, May 28. Not only did I work F8GGD, I heard two other French stations on CW here in Virginia (grid square FM18ap). They were in and out of the noise here for about 45 minutes before the band opened to the southeast. I then worked three stations in Venezuela, as well as stations in St Lucia, Bonaire and the Dominican Republic. Did you know that in seven of the past nine years on May 29, there has been E-skip between the Eastern US and Europe? In six of the past nine years, it has also happened on May 30. Check out this and other very interesting E-skip data from Kevin Gibeau, VE3EN. Lots of 6 meter ops in the Eastern US will have their beams on Europe today. The E-skip season has begun.”

And last, Daniel Eskenazi, K7SS, sent along this YouTube video of Raul Midon, KB5ZOT, and his brother Marco, N5ACR. This has nothing to do with propagation, but is very interesting. It has been out since 2009, but it is new to me.

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.