ZCZC AP14
QST de W1AW
Propagation Forecast Bulletin 14 ARLP014
From Tad Cook, K7VVV
Seattle, WA April 7, 2000
To all radio amateurs
SB PROP ARL ARLP014
ARLP014 Propagation de K7VVV
The sunspot number took a big leap this week, rising to 301 on Sunday. It has not been this high since November 12 of last year, when it was 324. Two days prior on November 10 meters the solar flux was 343, which is still the record for this cycle. The average sunspot count for the week was only up about 8 points though, and average solar flux was about the same as last week.
Solar flux is a measurement of 2.8 GHz energy from the sun, measured at the Dominion Radio Astrophysical Observatory operated by the National Research Council Canada in Penticton, British Columbia. You can visit the observatory web site at http://www.drao.nrc.ca/.
Sunspot numbers are calculated by multiplying the number of visible sunspot groups by 10, and adding the number of individual spots in all the groups. A multiplication factor is also used, and it differs for each observatory. You can see a complete explanation for sunspot numbers and their derivation at http://spacescience.com/headlines/y2000/ast05apr_1m.htm.
Geomagnetic indices have been high this week, with the average planetary A index almost double last week's number. The A index was in double-digits every day, with April 4 being the most disturbed. The planetary A index was 21, with planetary K indices as high as 5, and the mid-latitude index at 6 during the same period.
Coming up on Saturday and Sunday is the HF CW weekend for the Japan International DX Contest. Unfortunately, as this bulletin is being written on Thursday night, a major geomagnetic storm is raging. An interplanetary shock wave passed earth at 1730z on April 6, and Aurora have been spotted in North America as far south as North Carolina. The planetary K index for the end of thez day on Thursday was 8, and the A index was 56. The Boulder K index at 0300z on Friday is also 8. A severe geomagnetic storm began at 0100z on April 7.
For the next five days, Friday through Tuesday, the expected planetary A index is 30, 20, 15, 10 and 7. The predicted solar flux for the same five days is 175, 180, 180, 175 and 170. Solar flux is expected to rise above 200 again around April 14 and stay there well into the month of May.
Sunspot numbers for March 30 through April 5 were 225, 248, 287, 301, 252, 184 and 221 with a mean of 245.4. 10.7 cm flux was 205.5, 225.4, 222.9, 219.3, 215.4, 206.7 and 194.4, with a mean of 212.8, and estimated planetary A indices were 10 meters, 19, 14, 16, 12, 21 and 12, with a mean of 14.9.
Path projections for this week are for the Japan International DX CW Contest. Because the contest is for 10, 15 and 20 meters only, and for international stations to work Japan, the path projections will all be toward Japan and for 10, 15 and 20 meters only.