The K7RA Solar Update


All solar indicators were lower again for the second consecutive week. The average daily sunspot numbers declined more than 28 points from the week before to 40.9, while the average daily solar flux was off more than 18 points to 94.8. But looking at solar images from the STEREO mission, we can see a great deal of activity about to rotate toward us over the Sun’s eastern horizon. The whole “back” side of our Sun looks very busy.

Sunspot numbers for March 17-23 were 45, 35, 48, 47, 34, 31 and 46, with a mean of 40.9. The 10.7 cm flux was 90.1, 87.6, 88.8, 92, 101, 99.8 and 104.6, with a mean of 94.8. The estimated planetary A indices were 3, 2, 4, 4, 4, 6 and 10, with a mean of 4.7. The estimated mid-latitude A indices were 2, 2, 2, 4, 4, 5 and 9, with a mean of 4

The March 24 NOAA forecast for solar flux and the planetary A index sees solar flux for March 25-April 3 at 110, 115, 120, 125, 125, 130, 130, 130, 120 and 115. The planetary A index for the same period is predicted at 5 for March 25-29, 7 on March 30-31 and 5 on April 1-3. This indicates improving HF propagation for the near term, with geomagnetic indicators unsettled only very slightly, compared to recent very quiet conditions. Conditions should be good for the CQ World Wide WPX SSB Contest this weekend.

Geophysical Institute Prague has a forecast for geomagnetic conditions quite different from NOAA, predicting quiet conditions for March 25-27, unsettled to active on March 28, unsettled March 29-30 and quiet to unsettled March 31.

Carl Luetzelschwab, K9LA pointed out that the nanoTesla values for each level of K index mentioned in last week’s bulletin are actually for the Boulder, Colorado magnetometer, and the values are different for each observatory. He has a good description of how this all works here.

Jeff Hartley, N8II, of Shepherdstown, West Virginia, sent in this report on Saturday, March 19: “Despite the decline in solar activity, 12 meters has been consistently open to Europe every weekday this week, including some Russians, Latvia and Lithuania. As the flux has dropped off, the band has been opening later. The band was wide open to Europe at 1230 Monday (March 14), and Thursday and Friday (March 17-18) were good from about 1445 to past 1600. Fifteen meters has been consistently good to Russia with loud signals (RL3A S9+20, -30dB) and I even worked Central Asia -- including UK6, UK8 and UN3M (S9). I caught HS0ZDS on Wednesday right over the pole. The low K indices seem more important than the high flux for anything close to the pole, no big surprise. VU4PB had a good signal Thursday (March 17) on 17 meters from 1300-1500, and quite a few USA stations were getting through the European pile up for a new one”.

NASA has a video explaining the very low sunspot activity over the past few years. MIT’s Technology Review has an article about the double-peak of many sunspot cycles.

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.