The average daily sunspot numbers for the past week declined by more than half, nearly 52 points to 35.1, when compared to the previous week. Sunspot numbers for June 9-15 were 46, 35, 37, 16, 16, 48 and 48, with a mean of 35.1. The 10.7 cm flux was 87.5, 86.7, 84.5, 84.6, 86.6, 99.3 and 101.5, with a mean of 90.1. The estimated planetary A indices were 11, 8, 11, 9, 8, 7, and 7 with a mean of 8.7. The estimated mid-latitude A indices were 7, 7, 10, 5, 6, 7 and 9, with a mean of 7.3.

The average daily solar flux declined nearly 12 points to 90.1. Note that from Wednesday (the last day for the data reported at the end of this bulletin) to Thursday of this week, the solar flux went from 101.5 to 103.3, and the sunspot number rose from 48 to 62. NOAA and the USAF predict rising solar flux for the near term, with solar flux at 105 on June 17-20, 110 on June 21-23, 105 on June 24-26, then dipping below 100 after June 28. Predicted solar flux for ARRL Field Day weekend is 105 on June 24-26.

The predicted planetary A index for June 17-25 is 10, 8, 5, 8, 8, 5, 18, 15 and 10, followed by 5 on each day through the end of June. It seems that a recurring coronal hole may disturb our Earth’s geomagnetic field, with the maximum effect on June 23, two days before Field Day, but geomagnetic conditions should be very quiet by Sunday, June 26. Geophysical Institute Prague predicts quiet conditions for June 17-18, quiet to unsettled June 19, active conditions June 20 and unsettled conditions June 22-23. For some reason, they don’t offer a prediction for June 21.

The big news this week was the report issued from a meeting of the Solar Physics Division of American Astronomical Society, held at New Mexico State University in Las Cruces. The report is predicting another Maunder Minimum, many decades with hardly any sunspots. There seems to be a convergence of several lines of thought which all predict this, but fortunately there are dissenting experts. Douglas Biesecker of NOAA’s Space Weather Prediction Center, questions this hypothesis of disappearing sunspots. You can read his notes here (a slideshow accompanies his notes).

Peter Laws, N5UWY, of Norman, Oklahoma wrote: “On the morning of Memorial Day, May 30, I was alerted to a potential opening on the 2 meter band. I went to the radio room and tuned around. Sure enough -- a W8! I worked W8BYA in EN70, about 1230 km from me in EM15. My question is this: Was that a tropospheric ducting event, or was it sporadic-E? It seems to me to be long for tropo, but I don’t really know the upper end for tropo over land. Is there some rule of thumb that operators can use to try to determine which mode made the contact possible? As exciting to me as 2 meter DX contacts are, W8BYA was the only station I heard on the band.”

My suspicion is that the mode was sporadic-E, but I don’t know. Maybe some experienced VHF ops can lend an opinion on this.

The July 2011 issue of QST has an informative article by Joel Hallas, W1ZR, on pages 37-38 titled “Solar Indices -- What do they Mean?” In the article, Joel explains solar flux, sunspot numbers, the A and K indices and what they mean for the radio amateur. The article also gives a nice plug for this bulletin.

Lawrence, GJ3RAX, from the Isle of Jersey writes: “Last Friday, I had a phone call from GJ3YHU. That is not unusual, as he lives about a mile from me. This time he was down in Meze in the south of France, where he spends time regularly. He said that he had been hearing signals on 10 meters and wanted to see if there was a path between us. I was doubtful that it would be possible, as my typical sporadic-E QSOs are usually to the south of Spain, Gibraltar and North Africa. The south of France would probably be too close. We chose a frequency and tried, resulting in a QSO at 5/9 each way. That lasted for nearly 5 minutes before fading out.” Thanks, Lawrence!

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.