QST de W1AW
Propagation Forecast Bulletin 5 ARLP005
From Tad Cook, K7VVV
Seattle, WA February 4, 2000
To all radio amateurs
SB PROP ARL ARLP005
ARLP005 Propagation de K7VVV
Average solar flux and sunspot numbers were down over the past week, and geomagnetic indices were about the same as the week before. Average solar flux was down over 10 points to 138, and average sunspot numbers were off over 36 points to 99.
As projected in last week's Propagation Forecast Bulletin ARLP004, geomagnetic indices were active last weekend, with planetary A index for Friday through Sunday of 29, 25 and 11, compared to the predicted values of 25, 25 and 18. Planetary K index values were as high as 5 on Friday and Saturday, and the College K index, based in Alaska, was as high as 7, which indicates a severe geomagnetic storm.
For this weekend, expect moderate planetary A indices of 7, 7 and 10 for Friday through Sunday, rising to 15 on Monday. Geomagnetic indices should stay moderate until February 23-26, when the planetary A index could reach 20.
Predicted solar flux for Friday through Sunday is 155, 170 and 180, rising to 190 on Monday, 195 on Tuesday, and peaking around 205 on February 11-12. Solar flux is expected to drop below 150 again after February 18, and bottom out around 130 from February 23-25. There should be another solar flux peak around March 9-10, based on the rotation of the sun, which happens about every 27 days relative to earth.
Where are we now in the current cycle? A year ago this bulletin reported an average solar flux of 123.9 and 153.9 for the week previous. The average solar flux for the month of January was 159, for December was 169.8 and November was 191.5. The latest prediction from NOAA shows the peak flux value of the current solar cycle coming up in August of this year, but the value is only about 17 points higher than the monthly average forecast for this month.
W0NXS sent an interesting article from the Jet Propulsion Laboratory at the California Institute of Technology concerning repeatability in periods of solar magnetic fields. The article spoke of research which observed data over 38 years, and concluded that variations in solar magnetic fields repeat every 27 days and 43 minutes. The findings were published in the February 1 issue of the Journal of Geophysical Research. Additional information is at http://spacephysics.jpl.nasa.gov/pr/longitude.htm.
Another interesting article appears at the NASA Space Science News site at http://spacescience.com/headlines/y2000/ast03feb_1.htm. This shows some dramatic pictures from the Solar and Heliospheric Observatory detailing huge coronal mass ejections from the sun over the past week.
Sunspot numbers for January 27 through February 2 were 110, 96, 81, 90, 82, 107 and 127 with a mean of 99. 10.7 cm flux was 132.4, 152, 127.7, 132.7, 138.6, 138.1 and 144.4, with a mean of 138, and estimated planetary A indices were 12, 29, 25, 11, 6, 8 and 7, with a mean of 14.
This week's path projection will be from the center of the contiguous 48 U.S. states for Saturday, February 5.