Sunspot activity is up sharply this week, with the average daily sunspot number increasing more than 55 points to 89.9, while the average solar flux rose nearly 20 points to 103.1. Sunspot numbers for May 26-June 1 were 40, 65, 91, 89, 105, 132 and 107, with a mean of 89.9. The 10.7 cm flux was 82.7, 89.9, 101, 110.8, 111.9, 112 and 113.6, with a mean of 103.1. The estimated planetary A indices were 7, 11, 40, 32, 9, 13 and 12, with a mean of 17.7. The estimated mid-latitude A indices were 4, 7, 32, 17, 7, 10, and 9, with a mean of 12.3

The latest forecast shows solar flux at 115 on June 3, 110 on June 4-6, 105 on June 7-8, 100 on June 9-14, rising to 105 on June 15, and 110 on June 16-26. The planetary A index is predicted to be 12, 20, 15 and 10 on June 3-6, 5 on June 7-10, 8 on June 11-13, and 5 on June 14-21. The next period of high geomagnetic activity is projected for June 22-27, at 12, 22, 18, 18, 15 and 8. Note that ARRL Field Day for 2011 is June 25-26, which should be just after the predicted peak in geomagnetic activity, currently predicted for June 23. Geophysical Institute Prague sees unsettled to active conditions June 3-4, unsettled June 5, quiet conditions June 6-7 and quiet to unsettled June 8-9.

With the passing of May, we can look at some moving averages of sunspot numbers. The average daily sunspot number for the latest three month period -- March through May, centered on April -- was 74.4. The three month moving averages centered on May 2010-April 2011 were 16.4, 20.4, 23.2, 28.9, 33, 35.6, 31, 30.1, 35.3, 55.7, 72.3 and 74.4. The average sunspot number for May was 61.5, down somewhat from March and April. The monthly averages of daily sunspot numbers for January through May 2011 were 32.3, 53.5, 81.1, 80.8 and 61.5. Currently there are eight sunspot groups visible. Click here for a daily sunspot update.

Click here for an article titled “Mysterious Origins of Dark Sunspots Explained”. The journal Science has an abstract for the article mentioned in the Dark Sunspots piece here. Often with an account at your local library, you can log in and read the full text of the article. Another article similar to the Dark Sunspots article is here.

Don Tucker, W7WLL, who lives in Yachats on the Oregon Coast, writes: “The bands, particularly 20, have been so hot that I worked WAC and probably could have worked DXCC in one 24 hour period if I had tried!” Check out Don’s station and antennas here.

Bob Elek, W3HKK, of Johnstown, Ohio, reminds us of the upcoming ARRL June VHF QSO Party, which runs from 1800 UTC June 11 through 0300 UTC June 13. Bob writes, concerning 6 meters: “My own observation over 2010 and 2011 is that during last year’s E-skip season, there were many more broad strong openings 1000 miles out, and therefore, more double/triple hop openings than I’ve heard this year. In 2011, I often hear a handful of signals, often up and down into the noise, and that’s it. How much of this is based on antenna height, and very low angle of radiation I have no idea. But it just seems like 6 meters has been a far tougher E-skip band this year.”

Jon Jones, N0JK, of Lawrence, Kansas, writes: “On Sunday, May 22, 6 meters opened via multi-hop E-skip to the Caribbean most of the day. I worked FG5FR at 1928 UTC on 50.105 MHz. Franz was a solid 559 on my dipole. I heard numerous KP4s, 9Y4D and P43A. FJ/OS1T was on earlier and gave many a new country on 6 meters. I heard K0ZN in grid square EM28 working K0SBV (DM42) on May 29. K0ZN is in DeSoto, about 15 miles from Lawrence.”

Kent Doucy, N0IRM, of Galena, Missouri, had a nice 15 meter opening: “At 0454 on May 31, 2011 I found 5W1SA from Samoa calling CQ on 21.020 MHz with a great 579 signal. A little later at 0528, I was also able to work Brad FO/N6JA on Marquesas Island on 21.018 MHz; he was a little harder copy with a 519 signal. I didn’t hear anything else after that, but it was a nice short-lived late 15 meter opening to the Midwest.” See Kent’s antennas here.

Rudy Hanau, K2EVY, of Rye, New York, had some interesting comments regarding backscatter: “Most of us have run into HF backscatter at one time or another. In my experience, the other station and I find ourselves pointing our beams at some common point out of line with the direct path between us. But this incident was a bit different. On May 29, the SFI was 101 and the A index was 36. Not your most common set of conditions -- I suspect the geomagnetic activity associated with the high A is involved. Twenty meters was very sparsely populated and K6ZA’s S9 signal stood out. My QTH is Rye Brook, New York (FN31) and Barry is in Walnut Grove, California (CM87). His bearing should have been 280 degrees, just a bit north of west for me, and indeed it was. He was just finishing another QSO and I called him. He told me he had been working KL7 and was looking north! I swung north and lost him. He looked east and lost me. We were both S9 or better when our antennas were about 90 degrees to one another. We scratched our heads and looked every which way for another path but there was none.

“I signed after about 30 minutes and Barry went on to work another station. When working backscatter, we usually think of some far off reflecting area, such as aurora over Alaska or the pole. In mulling this contact over, the only explanation I can offer is that the reflecting area was very near Walnut Grove and was omnidirectional, like a vertical. If it was 50 or 100 miles north of Barry, it would be indistinguishable from Barry’s QTH for me, whereas Barry would have to point north to see it.

“Barry described his next contact as follows: ‘After our QSO I was called by a Laughlin, Nevada station southeasr of me, also same scenario. He was seeing me at normal northwestern direction. He was strongest to the north. Then, during the 30 minute contact, I found I could move the beam toward the east with no change in strength and then he began to peak more toward him and less to the north. By the end, he was 40 over at southeast, and no propagation to the north at all.”

There is a slightly revised solar cycle prediction from NASA. This month it says “Three consecutive months with average daily sunspot numbers above 40 has raised the predicted maximum above the 64.2 for the Solar Cycle 14 maximum in 1907.” Last month it said “Two consecutive months with average daily sunspot numbers in the 50s has raised the predicted maximum above the 64.2 for the Solar Cycle 14 maximum in 1907.”

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.