QST de W1AW
Propagation Forecast Bulletin 56 ARLP056
From Tad Cook, K7VVV
Seattle, WA December 31, 2001
To all radio amateurs
SB PROP ARL ARLP056
ARLP056 Propagation de K7VVV
Thanks to K9LA for writing last week's bulletin while I was vacationing in New York City. One of the highlights of my visit was watching the new star show at the Hayden Planetarium in the Rose Center for Earth and Space at the American Museum of Natural History. See http://www.amnh.org/rose/haydenplanetarium.html and http://www.amnh.org/rose/index.html for more information.
This bulletin was prepared Sunday night to update the solar and geomagnetic data.
Average daily solar flux was up nearly 34 points for the December 20 through 26 period, compared to December 13 through 19. Solar flux is predicted at 250 for December 31 and January 1, 245 for January 2, and 255 for January 3 and 4.
A coronal mass ejection on December 28 was not directly aimed at earth, but caused a rise in geomagnetic activity on December 30. Planetary K indices rose as high as 4. The planetary A index is predicted at 20, 15 and 10 for December 31 and January 1 and 2.
WD4NIT asked about the holographic technique used for detecting sunspots on the sun's far side. You can read a very interesting explanation of helioseismic holography on NASA's web site at http://spaceweather.com/glossary/farside.html .
We get email occasionally asking for more information on some of the terms used in this bulletin. This has been covered from time to time, and you can find a large list of old bulletins on the ARRL web site at http://www.arrl.org/w1aw/prop/ .
A recent explanation was in Propagation Forecast Bulletin ARLP038, available at that same URL. The propagation chapter in any recent edition of the ARRL Handbook is also an excellent resource.
Sunspot numbers for December 20 through 26 were 171, 215, 234, 220, 176, 246 and 290 with a mean of 221.7. 10.7 cm flux was 221.1, 234.3, 242.8, 254.6, 274.5, 258.8 and 267.8, with a mean of 250.6, and estimated planetary A indices were 5, 11, 8, 7, 19, 8 and 7 with a mean of 9.3.