The K7RA Solar Update
Last week's bulletin again mentioned briefly appearing sunspots and it happened again this week. For just two days, another Solar Cycle 23 spot appeared, number 1014. The latitude of the spot was consistent with an old and fading solar cycle. As this period of quiet Sun drags on, statistic based projections of a return to solar activity continue to be pushed out. Sunspot numbers for March 5-11 were 0, 12, 12, 0, 0, 0 and 0 with a mean of 3.4. The 10.7 cm flux was 69.2, 69.1, 69.1, 68.9, 69.1, 68.8, and 68.9 with a mean of 69. The estimated planetary A indices were 3, 2, 1, 8, 2, 3 and 3 with a mean of 3.1. The estimated mid-latitude A indices were 3, 0, 0, 7, 1, 3 and 2 with a mean of 2.3.
Early Friday morning, the planetary K index is rising to 5, then 4. This is from a stream of solar wind bearing down upon us. NOAA and the US Air Force predict a planetary A index of 15 for today (March 13), 10 for Saturday then back to 5. It's tough to forecast this far out, but they show that active region returning on April 9.
Geophysical Institute Prague projects unsettled conditions for March 13-14 and quiet conditions March 15-19. On March 10 at 2333 UTC, the Australian Space Forecast Center released a bulletin predicting "increased geomagnetic activity expected due to coronal hole high speed wind stream from 13-14 March 2009." The Center has 26 e-mail alert services that anyone can subscribe to.
Chuck Zabreskie, KE5HPY, of Houston, Texas, wrote with an anecdote about last weekend's propagation: "Thought I'd mention a pleasant surprise last Saturday afternoon (2100-2200 UTC) during the recent ARRL International DX Phone Contest. My rig is 100 W into a 35 foot OCF (off-center fed) dipole -- nothing fancy. I need to look where the others aren't piled up. Twenty meters was busy as you'd expect, so I took a look at 15 meters after looking at W6ELProp. I got great signals from Peru, Argentina and Brazil (among others), but little heard to the north of my location in Houston, Texas (30 degrees North). Feeling lucky, I looked at 10 meters and also had great copy from Argentina and Brazil until 2230. Nothing in W6ELProp suggested that should be where it appeared. Again, nothing heard to the north of them or here, and relatively few US operators coming back to their CQs. Seemed like a pipeline between Texas/Arizona into that zone. Nothing like a contest to demonstrate what the bands permit. I'll be calling CQ on 10 meters this Saturday. Is this a seasonal effect due to the equinox? Is it common to see a small zone on either end of the pipe?"
I thought I would check into Chuck's results using W6ELProp that should factor in the equinox. Although the program is meant to be used with the predicted smoothed sunspot number for the month, I used a sunspot number of 12 -- the actual daily sunspot number for March 6-7. Chuck is near Rice University in Houston and actually sits to the south of the 30th parallel, at 29.725 degrees North latitude.
Using March 7 with a path to Brazil at 15 degrees South, 54 degrees West, I show that as a good time for propagation on 15, and even 10, and especially 20 meters, using the exact coordinates for Chuck's location. But I wonder why other North American stations weren't working the South America stations? But it is interesting that W6ELProp shows much less favorable conditions for other stateside areas into Brazil, even from Dallas, which is around the 33rd parallel. Chuck and I will have to compare our results using W6ELProp.
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.