The K7RA Solar Update
ARRL Headquarters is closed for Good Friday on March 21, so this bulletin is coming out a day early, and on the vernal equinox. We had a few more days with visible sunspots over the past week. Sunspot numbers on March 15-17 were 12, 12 and 11. Over the past month, we seem to have a single sunspot appear for a few days, then fade away or rotate out of view, then another pop up after four or five days. Take a look at sunspot numbers since January 1.
Projection for the near term is planetary A index of 5 for March 20-24, then 10, 20, 25, 20 and 8 for March 25-29. There are similar returns to planetary A index of 25 predicted for April 5, April 23 and May 2, but otherwise quiet. Geophysical Institute Prague predicts quiet to unsettled conditions for March 21, quiet March 22-24, unsettled March 25 and active March 26-27.
Dale Drake, W7GMY, of Lake Helen, Florida asks "Just a curious question on the Solar Cycle numbers. How do they come up with cycle numbers? Cycle 24 would indicate at 11 years per cycle, that it is 253+/- years in recording the cycles". Dale was surprised to learn that daily sunspot records do stretch way back over hundreds of years, and Cycle 1 in fact peaked a quarter century prior to America's Revolutionary War. Check the WM7D Web site to see graphs of Solar Cycles 1-23.
Paul Kiesel, K7CW of Tahuya, Washington, sent a fascinating article translated from the September 2006 issue of Japanese radio magazine CQ Ham Radio. Han Higasa, JE1BMJ, wrote about surprising long distance 6 meter polar propagation from Japan to Europe with Sporadic-E at the summer solstice. He doubts this is multi-hop propagation, even though the long distance suggests this, because the signals don't seem to be as dispersed or scattered as one would expect from multiple hops. Instead, JE1BMJ posits that the mechanism is PMSE, or Polar Mesosphere Summer Echo, a radar echo phenomenon. Rather than taking several hops, the signal would be refracted through the E-layer for a long distance following the curvature of the earth, before exiting and being heard in Europe.
There was a great deal of mail this week on possible auroral-E propagation in the summer on 6 meters, when the K index is high and there is backscatter via aurora. But while the normal auroral communications sound distorted, E-layer propagation will arise which is not at all distorted.
K7CW reports an opening from the Pacific Northwest on 6 meters to W4 and W5 on October 20, 2007. There was aurora, but at the same time this propagation over long distance that did not seem to be via aurora, sounding very strong and clear. K7CW wonders if this might be an example of Snell's Law, which addresses refraction along an interface between two mediums.
Ray Perrin, VE3FN, of Ottawa, Ontario wrote about possible auroral-E propagation while operating from the arctic in Iqaluit, on Baffin Island at Frobisher Bay in Nunavut (63.75 degrees North, 68.52 degrees West). Ray made several business trips there in 1999-2002. Iqaluit is where the VE8BY 6 meter beacon is located, in grid square FP53. For 6 meters, Ray used a wire dipole tied to a rock thrown from his bedroom window in his temporary housing, and another dipole made from two telescoping antennas mounted on his porch.
Ray writes, "I worked many stations in North America using these simple antennas. For example, during two weeks in July and August of 2001, I worked into VO1, VE1, VE2, VE3, W1, W2, W3 and W4 as far south as North Carolina. I also worked some in W8 and W9 and one station in Colorado. There didn't appear to be a distinct skip zone. And about 40 percent of the evenings, I heard the OX3SIX beacon (on 50.012 or so) for about 45 minutes at 0000 UTC. It would roll in on Auroral E -- no distortion. I always called CQ when I heard the beacon, but no QSOs. I later received a report from a station in northern Scotland saying he thought he had heard me. It is likely he did as I was calling CQ at the time. Again, this was all Auroral E -- no 'buzz'. In February 2002, I worked SP2NA on F layer using the wire dipole."
Ray's last trip to Iqaluit was November 2002. He used a 2-element Yagi for 6 meters. "During that trip I worked OX3SA on auroral E. Later, I also worked into VE6 (DO33) on auroral E. By the way, the evening I worked VE6 (a Saturday), I was hearing beacons in VE6, VE4 and northern W0 for about 3 hours, but I was only able to dig up one QSO! I was simultaneously calling CQ on 144 MHz, but nothing heard. At noon the next day (Sunday) the band opened briefly on F layer to southern Florida -- about 3000 miles."
Ray continued: "Except for a few QSOs on F-layer, all my contacts appear to have been on auroral E. The signals were not distorted as they would have been on straight aurora. I would typically wait for a day when the K index went up to 5 and the band would often open in the evening, especially in the summer. I have heard the VE8BY beacon many times from Ottawa on auroral E, but never when the band was open on 'buzz' aurora. And when we do have 'buzz' auroral signals coming in on 6 meters, I have never heard VE8BY/b."
Ray wrote, "So what is the cause of auroral E? Is there any relationship to the occurrence of auroral E and the sunspot cycle? Some have suggested that auroral E may occur when the aurora becomes weaker. If this were so, then one would expect to hear auroral E on, say, 50 MHz when there is 'buzz' aurora on 28 MHz. In other words, as the MUF rises, one would first experience auroral E and then straight 'buzz' aurora. But if this were true, one would expect to hear auroral E frequently on 50 MHz (at mid latitudes) when, in fact, I believe it is quite rare at mid latitudes. And one would expect to observe auroral E quite frequently on 144 MHz when 50 MHz is open on 'buzz' aurora, but it isn't intense enough to propagate 'buzz' aurora on 144 MHz. Once again, this doesn't wash as auroral E on 144 MHz seems to be very rare at mid latitudes. I once thought that ordinary 'buzz' aurora was related to paths that were more or less east/west whereas my QSOs from FP53 (auroral E) were predominantly north/south. However, my QSO with OX3SA and frequent reception of the OX beacon involve east/west paths -- and they were all auroral E."
Carl Luetzelschwab, K9LA sent a lot of great material about auroral E propagation, but there isn't room to address it in this bulletin. Go to Carl's Web site and click on the titles "Alaska to EU on 6m," "More Alaska to EU on 6m" and "Summer 6m Es Probabilities" to download pdf documents he wrote for his propagation column in World Radio.
Finally, no room to talk about a very important development for HF propagation, the first day of spring, which is today. This is a great time for worldwide HF propagation, as all of the Earth is receiving a maximum amount of solar radiation, the same in both southern and northern hemispheres.
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 in The ARRL Letter. Check 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.