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 Previous: Surfin': Hamming on the Go | ![Next (later) Story](/images/sty-up.gif "ARRL Withdraws "Regulation by Bandwidth" Petition, Plans to Refile"){kind=small} Next: ARRL Withdraws "Regulation by Bandwidth" Petition, Plans to Refile |
SEATTLE, WA, Apr 27, 2007 -- Sunspots have reappeared over the past few days after six days of nothing. So far in April we've seen 18 days with zero spots, but a large sunspot, Number 953, now is rolling into view. A solar wind stream also is expected to hit Earth, causing a geomagnetic upset on Saturday, April 28. The Australian Space Forecast Centre predicts quiet-to-unsettled conditions April 27, active-to-minor storm conditions April 28, and active conditions April 29. The US Air Force predicts the planetary A index from April 27 through May 1 at 5, 25, 15, 10 and 8. Similar predictions from Geophysical Institute Prague give us quiet conditions April 27, active April 28, unsettled to active April 29, unsettled April 30, quiet to unsettled May 1, and back to quiet May 2-3.
There's been a lot of news this week regarding the solar minimum and predicted solar maximum. On April 25, a Solar Cycle 24 Prediction Panel consisting of members from NOAA, NASA and other agencies looked at all available predictions, attempted to reach consensus and released a statement. It looks like the minimum between cycles 23 and 24 may not occur for another year, until March 2008, a year later than recently reported. The accuracy is expected to be plus or minus six months. The peak of Cycle 24 is expected to occur in October 2011 if there is a large solar cycle, and August 2012 if it's a small cycle.
Many people sent links to articles about this. Frank Donovan, W3LPL, in Maryland sent a couple of links, including one to a graphic representation of a range of predictions. Also see "Solar Cycle 24 Prediction" from the Space Environment Center, which includes PowerPoint presentations. The Associated Press also ran a news story, and Space.com posted an article, "Sun's Next Stormy Cycle Starts."
We received a large volume of mail this week and hope to get to more of it next time. Among reports was some unusual 6 meter backscatter propagation observed on April 21 by Bill Van Alstyne, W5WVO, in New Mexico. I'll let Bill describe it:
"Greetings from New Mexico, DM65. Just finished a very unusual opening off of a pre-season Es cloud in northern Mexico, approximately 2315Z-0100Z. Many central Mexican stations in XE1/XE2 with 59++ sigs, but the real news was the amazing strength of the backscatter signals coming in from Arizona, New Mexico, Utah, Texas, and California, all peaking with the beam pointed due south. Was able to work a couple of new close-in grids in AZ, as well as many other grids I already had. Strongest backscatter signals were from Bob, W7UT, in southwest Utah; Bud, N7CW, in Prescott, AZ; and Tommy, W7RV, in Scottsdale, AZ. All were consistently 56/57 until the propagation began to weaken around 0030Z."
Bill continues:
"This is by far the strongest backscatter I've ever heard on 6 M. As a rule, Es clouds (due to their very thin, flat architecture) are very poor backscatter producers; the only previous backscatter I've ever worked off of 6M Es was extremely weak. This backscatter propagation was ragchew quality, and lasted virtually without QSB for over an hour."
Also this week we saw some of the early 3D images from the NASA STEREO satellites. To view in 3D, you need glasses with a red filter covering the left eye and a cyan filter over the right eye. I was able to locate a pair for less than a dollar at Science, Art and More, a shop in my neighborhood that sells products for science education.
I must admit I was a little disappointed, but only a little. At the distance these solar images are taken, the depth effect of the sun shows it as very close to a perfect sphere, in my estimation. Perhaps I was hoping for detailed looks at the surface with exaggerated three-dimensional effects that would enhance the perception of depth and detail. But I have no doubt that the images shown on that page are probably accurate, more so than what I had imagined.
For More Information
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page and the article "The Sun, the Earth, the Ionosphere: What the Numbers Mean, and Propagation Predictions," by Carl Luetzelschwab, K9LA. An archive of past bulletins is on the ARRL Web site. The propagation charts that formerly appeared in QST now are available on the QST Propagation Charts page on the ARRL Web site.
Weekly Sunspot Numbers
Sunspot numbers for April 19 through 25 were 0, 0, 0, 0, 0, 0 and 14, with a mean of 2. The 10.7 cm flux was 68.3, 68.5 68.7, 68.9, 69.1, 73.2, and 76.5, with a mean of 70.5. Estimated planetary A indices were 6, 3, 2, 10, 18, 4 and 5, with a mean of 6.9. Estimated mid-latitude A indices were 4, 2, 2, 8, 10, 5 and 4, with a mean of 5.
Amateur solar observer Tad Cook, K7RA, 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. Readers may contact the author via e-mail.
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