Solar activity declined this week: The average daily sunspot numbers were off by more than 13 points to 75.1, while the average daily solar flux dropped over 32 points to 102.1. The solar flux dropped barely below 100, but rounded up to 100 as shown on the NOAA SEC site. The next short-term peak in solar flux is expected at the 135 level for April 3-6. The predicted solar flux for March 23-25 is 100, 105 on March 26, 110 on March 27, 115 on March 28-29, 120 on March 30, and 130 on March 31 through April 2, then 135 on April 3-6, and 130, 120, 115 and 105 on April 7-10, 100 on April 11-15, 105 and 110 on April 16-17, and 100 on April 18-22.

Sunspot numbers for March 15-21 were 85, 104, 89, 54, 58, 74 and 62, with a mean of 75.1. The 10.7 cm flux was 110.6, 98.5, 102.4, 102, 101.8, 99.6 and 99.9, with a mean of 102.1. The estimated planetary A indices were 30, 20, 20, 10, 10, 4 and 4, with a mean of 14. The estimated mid-latitude A indices were 24, 17, 15, 11, 8, 4 and 4, with a mean of 11.9.

The predicted planetary A index is 5 on March 23-27, 10 on March 28, 8 on March 29-31, 5 on April 1-2, 8 on April 3-4, 5 on April 5-9, then 12, 5, 5, 15 and 10 on April 10-14, and 5 again on April 15-23, then 10 on April 24, 8 on April 25-27, and back to 5 on April 28-29.

Even with the decline, new sunspot groups were popping out this week. On Thursday, March 15, sunspot group 1435 appeared; the next day, 1436 emerged, followed by 1437 on March 17. On March 18, 1437 disappeared, followed by 1436 on March 19. On March 20 two new groups -- 1438 and 1439 -- appeared. On March 21, 1439 disappeared while 1440 emerged. On March 22, three new sunspot groups -- 1441, 1442 and 1443 -- appeared.

Fred Glenn, K9SO, of Palatine, Illinois sent in an interesting article about neutrino communications. Of course, with a 0.1 Hz data rate (would a dit take 10 seconds to transmit?) and a 170 ton detector, this medium requires a little work.

Howard Lester, N7SO, pointed out that the link we gave in last week’s Solar Update to Alan Friedman’s images show photos taken in Buffalo, not Brooklyn. Also, I had a real “doh!” slap-my-forehead moment when he pointed out that pictures of the Sun are not affected by light pollution from city streetlights and other urban sources that bedevil astronomers searching the night sky.

In a message titled “Propagation Weirdness,” Jim Hadlock, K7WA, of Seattle, Washington on March 22 wrote: “This morning, while chasing European stations on 17 meter CW, I worked 9M6YBG (at 1614 on 18.080 MHz) -- and it wasn’t the first time. Last year on March 30, I worked him at 1627, about midnight his time. I guess it's ‘anything can happen day!’”

I thought that might be unusual if Jim was beaming Europe, as the short path antenna heading from Seattle to Europe is about 30 degrees. Short path toward East Malaysia is about 300 degrees and long path about 120 degrees. But then it occurred to me that Jim may not have been using a highly directional antenna.

Doing some crude propagation modeling with W6ELprop, the time that Jim contacted 9M6YBG is actually the beginning of a second opening for the day on 17 meters at this time of year in early spring. The model shows a brief opening from 0600-0730 UTC (11:00 PM PDT until 12:30 AM), but the second opening looks better, after 1600 UTC, very strong and reliable through 1930 UTC.

Yet another article about our Sun popped up the other day, and I like the way it describes our Sun’s corona as “covered and bound up with strong magnetic fields that are ropy and twisted in nature,” like “a writhing mass of snakes holding in the surface of a globe.

A story and photo out of Fargo, North Dakota describes a doctoral candidate’s effort to accurately predict sunspot activity.

On March 17, Jeff Hartley, N8II, of Shepherdstown, West Virgini,a wrote: “It seemed like disturbed conditions most of the week. The solar flux index really took a nose dive today compared to two or three days ago -- only 100 with the K index currently at 2. Fifteen meters was almost dead to Europe in the 1400 hour, which is usually about the best hour. Instead, I only heard just a few rather weak Mediterranean area stations. The Russians on 20 were ‘watery,’ fluttery, especially from Asia, but I did log a few Western Siberian stations, mostly from Zone 17. Even the Moscow area stations were weak, unless beaming toward USA.”

Finally, check out a couple of interesting links. Click on “Solar” and then the “Terrestrial” links. They show some interesting indicators for geomagnetic activity and solar flux.

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.