The K7RA Solar Update


Our Sun is still not producing any sunspots. As mentioned in previous bulletins, the peak of the last Solar Cycle was a double peak, so perhaps we are in the midst of an extended bottom. Sunspot numbers for August 7-13 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0. The 10.7 cm flux was 66.1, 65.5, 65.5, 65.6, 65.7, 65.2 and 65.3 with a mean of 65.6. Estimated planetary A indices were 4, 4, 18, 13, 7, 6 and 5 with a mean of 8.1. Estimated mid-latitude A indices were 3, 3, 16, 9, 6, 6 and 3 with a mean of 6.6.

Roger Lapthorn, G3XBM, of Cambridge, England, reported these observations about 6 meter: "Following on from comments in the August 8 propagation bulletin, I'd like to mention August 6 when, here in the UK on just a small VHF collinear, I heard both D4C and K1TOL on 6 meters CW. The Cape Verde station was working a string of EU stations and peaked at 539 with me. Lefty, K1TOL (who I worked last year on 6 meters with just 2.5 W!) was 569 and a solid signal for 15 minutes. A little later I was able to work N2MM on 10 meters SSB with just 10 W and a halo antenna. My summary is that 6 meters (and 10 meters) truly is a magic band if one can hear such DX on such a simple antenna -- and at sunspot minimum. Last year's experience of working K1TOL confirmed that it is possible to work such DX too with a bit of luck and decent Sporadic-E."

The following is from Scott Bidstrup, WA7UZO, and is so interesting that I thought I should include it in its entirety:

"I live in Costa Rica (EK70rc); at this low latitude, propagation is significantly different than in the States. I have been having a lot of fun exploring those differences; I recently downloaded and installed BeaconSee to watch propagation from the NCDXF/IARU beacon network. And I have noticed something you might find to be quite interesting.

"While monitoring the NOAA space weather Web site, I discovered that when a boundary crossing occurs, there seems to be a mode switch in the propagation I see here in Costa Rica. If the Bz component -- the z axis of the solar wind interplanetary magnetic field -- is strongly positive on 20 and 15 meters, I see fairly strong signals from the 4U1UN beacon in New York and moderately strong signals from the OA4B beacon in Peru. I can also see a weak signal from W6WX and occasionally KH6WO, and from the ZS6 and 5Z4 beacons in the early morning as well.

"When a boundary crossing occurs, it's like someone throws a switch -- over three or four minutes, 4U1UN fades, the W6 and KH6 beacons disappear and OA4B booms in. The bands will get somewhat noisy until the Bz becomes settled in the decidedly negative, at which point the noise will subside and the OA4B beacon will become so strong I can even hear it in the 100 mW mode. But I can hear practically nothing else on the band, and see the 4U1UN beacon only very weakly. When the bands are in this mode, 10 meters is open to South America, but only to stations in an arc across the middle of the continent from Santiago to a range from Buenos Aires to Sao Paulo -- no other stations need apply.

"This bimodality seems to be inversely correlated to solar wind speed: The higher the wind speed, the smaller the effect. It seems to be positively correlated with the proton density -- the stronger the proton flux, the stronger the signals from South America."

Thanks to Carl Luetzelschwab, K9LA, for writing the excellent bulletin last week.

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.