The K7RA Solar Update
Last week's sunspot group was only visible for three days, December 10-12. The average daily sunspot number for all of 2007 was 12.8; if we see no sunspots for the rest of 2008, the average for this year will be 4.7. By comparison, the yearly averages of daily sunspot numbers during the last solar minimum (1995-1997) were 28.7, 13.2 and 30.7. This solar minimum is much lower than the one about 12 years ago.
Sunspot numbers for December 11-17 were 12, 14, 0, 0, 0, 0 and 0 with a mean of 3.7. The 10.7 cm flux was 70.2, 71, 69.7, 68.8, 68.9, 69.4 and 68.8 with a mean of 69.5. The estimated planetary A indices were 3, 2, 1, 0, 1, 4 and 5 with a mean of 2.3. The estimated mid-latitude A indices were 4, 2, 1, 1, 1, 4 and 3 with a mean of 2.3.
Geomagnetic conditions have been stable and quiet this week, very nice for those lower HF frequencies during the long nights. As you can see, there have been many very quiet geomagnetic periods over the past few months. That table is based on the calendar quarter, so check here for the previous 30 days if you are reading this later than the end of 2008, only 12 days after this is written.
The daily A index (a linear scale, calculated from the eight daily K index readings, which are on a logarithmic scale) gives an interesting comparison to the last solar minimum. We can check those weekly averages beginning with the October 11, 1996 bulletin, when we began presenting the planetary A index at the suggestion of Robert Wood, WB5CRG (now W5AJ), of Midland, Texas.
Go to here and compare the weekly averages with current averages here and you can see that during all those weeks of zero sunspots, geomagnetic activity was much higher. It is also interesting to note how quickly sunspots returned toward the end of 1996 after those long weeks of no spots.
The outlook from USAF/NOAA shows solar flux below 70 through December 25, then at 70 from December 26-January 8. Perhaps we may see more sunspots during this period. The same prediction shows planetary A index of 5, except for December 22-23, when it rises to 10, then 8, and then December 31 to January 2, with planetary A index of 8, 10 and 10. Otherwise, all could be quiet. Geophysical Institute Prague predicts quiet conditions for December 19-21, unsettled December 22-23, quiet to unsettled December 24 and quiet again on December 25.
The 2008 winter solstice officially occurs in the Northern Hemisphere at 1204 UTC on December 21. This is during darkness on the West Coast of North America, where I am, so my Saturday night through Sunday morning should be the longest night of the year. This far north (Seattle), the Sun will set at 4:20 PM (0020 UTC Sunday) on Saturday, and rise at 7:55 AM (1555 UTC) on Sunday, December 21. This is 15 hours and 35 minutes from sunset to sunrise, nearly two hours longer than the same night in South Florida and almost two and a half hours longer than the same night on the southern tip of the island of Hawaii. Tierra Del Fuego -- at the southern end of South America -- will have a very short night this weekend, about six hours and 40 minutes from sunset to sunrise as it enters the Southern Hemisphere's summer season.
With all of these quiet days, there is still fun to be had and things to explore on HF. Two weeks ago on December 5, Chuck Hooker, VE3CQH, of Orangeville, Ontario, reported: "The low sunspot cycle doesn't seem to affect me and Bill, K4KSR (of Yorktown, Virginia). He added to his DX total during the CQ World Wide CW DX Contest using a K1 transceiver, and he and I communicated during our first sked -- and my first QSO in more than a year -- earlier this week on 40 meters. I called; he answered. Bill uses 5 W or (usually) less to a hidden antenna; I applied 1.2 W from a crystal-controlled Little Joe through a home-brew antenna tuner to a G5RV about 20 feet up (but downhill from the shack). Bill gave me a 579 at 1900 UTC."
In last weekend's ARRL 10 Meter Contest, we still saw activity, despite the fading sunspots. Dan Eskenazi, K7SS, of Seattle, Washington, reported some scattered openings on Saturday to the south and southwest, some nice sporadic-E propagation into Colorado and double-hop propagation further east.
Terry Oldham, KH6MT, of Grand Island, Florida, reported hearing good signals from the East Coast and into Ohio, Michigan, Arkansas and Louisiana, but not to Texas.
Vic Woodling, WB4SLM, of Centerville, Georgia, said the 10 meter propagation was unique, and while he put a small effort into the contest, "there was something for everyone. Friday night, December 13, ground wave was awesome. Can't say as to why, but could very easily work stations 200 to 300 miles. Found conditions close to what one will see on 6 meters. I decided to check 160 after about an hour from the start of the 10 Meter Contest and logged UT3UA amongst others in EU. Went back to 10 meters at 0321 and had some very unusual prop into the Northeast. It may have been Es, but let me explain: The conditions sounded like meteor scatter with an E coupling. CW signals were great. Hearing very strong bursts with long decay and the residual was there for several minutes. For example, K1ZZ was one call 100 W and I heard him many times over the next few hours in and out of the noise. Around 0400 UTC, the band shifted to the 0s. I stayed up until about 0530 UTC and continued working 2s & 3s. Saturday afternoon, I got some Es to 8 and 9 land.
"Sunday, December 14, from 0100 to about 0200 UTC, there was very strong ground wave again, but not as long a distance as the night before. Ten meter Es to W0SD, but the E was sporadic. Checked 160 and logged OK2PAY, SM5EDX, UR0MC and UX1UX; I copied but did not work EL2DX. I went off the air at 0400 UTC, but was back on at 1624 UTC and the band was open Es to all call areas. I didn't have to move the antenna, as there were very strong signals. Around 2015 UTC, the PYs in Brazil appeared -- every PY in the country must have been on, along with OA (Peru), then a shift at 2047 UTC to LU9 land (southern tip of Argentina). Signals were in reality 55 to 57 (disregarding the usual exchange!), but no problems working them very quickly. In the middle of the DX, stations in North Florida and South Florida suddenly appeared with 20+9 signals (very short skip). Went over to 6 meters quickly and got a partial on WP4 and some Northeast stations, but I didn't stay, as I wanted the DX on 10. At 2120 UTC, the band shifted again and went into the scatter mode. I worked some more GA, AL, SC and NC stations on groundwave and dropped up to 160 after the 0000 UTC hour.
"On Monday after the 10 Meter Contest was over, 160 meters was great for us with a dipole and couple hundred watts. I logged RK3AWL and his signals were an honest 599 on the meter; mine weren't so good at 449. I worked GW3YDX, ES5QX, LA5HE, SM2LIY and OH2BO. I was first to hear him, but with his 'QRZ?' to my call, it created an orange glow of EMP radiation out of the Northeast, thus prohibiting me from making the contact.
"Overall, I thought the 10 meter band was a pleasant surprise. I wasn't expecting much, but what I'll call 'meteor scatter with residual' really got me going, and for me it's always been the propagation and the wonder of it that has kept me in radio. Anyone can buy a kit, have the biggest and best, but it's the absolute wonder of radio wave propagation which keeps the headsets on."
Thanks, Vic! There is much more to report, and this is running very late. I am between snowstorms in Seattle, and it is almost noon in Newington where a blizzard is about to blow in, so I must put this to bed. Expect to read more about meteor scatter in the next bulletin, as well as a hole in the terrestrial magnetic field and a thin ionosphere. This may come out as an extra on Monday, December 22, in addition to the following Friday bulletin on December 26.
Stay warm and safe!
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.