The K7RA Solar Update


Eight new sunspot groups appeared this week, but the average daily sunspot number declined four points to 71.1; the average daily solar flux rose by less than two points to 103.7. Sunspot numbers for March 22-28 were 86, 74, 65, 84, 56, 63 and 70, with a mean of 71.1. The 10.7 cm flux was 102.4, 104.8, 102.7, 101.3, 102.4, 105.6 and 107, with a mean of 103.7. The estimated planetary A indices were 6, 6, 10, 4, 4, 12 and 12, with a mean of 7.7. The estimated mid-latitude A indices were 6, 5, 9, 4, 4, 15, and 10, with a mean of 7.6.

On March 22, three new sunspot groups appeared, numbered 1441, 1442 and 1443. Two more groups appeared the next day -- 1444 and 1445 -- and 1442 vanished from view. On March 24, group 1441 disappeared and on March 25, new group 1446 emerged. On March 26, groups 1440, 1443 and 1446 faded away, but 1442 -- not seen since four days earlier -- re-emerged. On March 27, group 1444 disappeared and 1447 appeared, and on March 28 new group 1448 arrived.

For the short term, the planetary A index is predicted to be 5 on March 30-April 9, then 12 on April 10, and back to 5 on April 11-12, then 15 and 10 on April 13-14, followed by 5 on April 15-23. A similar pattern appears way out in May, when the planetary A index is predicted at 12 on May 7, then 15 again on May 10. It’s a good guess that this is probably based on the rotation of the Sun relative to Earth, predicting that an active magnetic area could appear again 27-28 days later.

The solar flux prediction shows flux values of 120, 130 and 135 on March 30-April 1, then 140 on April 2-6. On April 7-11, the predicted solar flux is 130, 125, 120, 110 and 105. On April 12-15, the predicted solar flux is 100. It then goes to 105 and 110 on April 16-17 and back to 100 on April 18-21, then 105 on April 22-23, 110 on April 24-25, 120, 125, and 130 on April 26-28, and 135 on April 29-30. Another peak at 140 is predicted for May 1-3.

Q-up Now has a fascinating new set of real-time propagation tools, developed by a team associated with the Utah State University Space Weather Center in Logan, Utah. They use a real-time model of the ionosphere called GAIM (Global Assimilation of Ionospheric Measurements), which is updated every 15 minutes with 10,000 global TEC (Total Electron Content) measurements to simulate the F layers.  Then they use the ABBYNormal Model to model the D and E layers, and the two models are combined to give a complete representation of the global ionosphere.

You can create a free account for yourself on the website and use it for up to two weeks without charge. After that, subscriptions are available. On the first page you will see NVIS maps for Near Vertical Incidence Skywave propagation. These are not quite ready yet, and currently the maps shown are several days old. Most interesting is the HF Availabilityarea, in which you can model real-time propagation for the frequency of your choice between any two points and beyond out to the antipodes. You can use latitude/longitude coordinates, but I found it easiest to just copy grid square data from call sign servers. This tool also works on 160 meters, which the propagation prediction programs that many of us use do not. Of course the major difference with this tool is that it tells you what the propagation should be over any path right now, but they are planning on offering a predictive tool. Have fun!

Torsten Schwarz, XE2/K5TOR, wrote: “On Sunday, March 25 at 1500, I was surprised that I was hearing a US FM radio station on my radio (103.1 MHz) as clean as if it were a local station. At that time, I was driving from my home in Saltillo (DL95ml) to work and all that time the signal was very strong. I also managed to transmit APRS Packet with no problem (Saltillo has no IGate or digi) you can look it up on (Call: K5TOR-9). I have no idea what propagation that was as it was at least 30min and there was hardly any fading.”

Using this site, I searched for stations on 103.1 MHz in Texas. A likely candidate was KPAS FM, and the distance to Torsten’s grid square from the transmitter site was 530 miles. Perhaps some solid E-layer skip was helping it along that day.

Pete Heins, N6ZE, of Thousand Oaks, California wrote: “After various parts of the US experienced long haul 6 meter DX to South America and the Pacific on March 28-29, I worked FK8CP at 0342 on March 29 on CW. I did not ID any other DX stations, but I heard a few other Southern California stations make a few contacts. My rig is 100 W with a 5 element Yagi up only 14 feet.”

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.