ZCZC AP15
QST de W1AW
Propagation Forecast Bulletin 15 ARLP015
From Tad Cook, K7RA
Seattle, WA April 8, 2004
To all radio amateurs
SB PROP ARL ARLP015
ARLP015 Propagation de K7RA
This bulletin is going out a day early because ARRL Headquarters will be closed for the Good Friday holiday.
Both solar flux values and sunspot numbers dropped this week. Average daily sunspot numbers declined over 46 points and solar flux was down nearly 20.
Solar flux is expected to rise over the next couple of days. Predicted solar flux for Thursday through Monday, April 8-12, is 105 for Thursday and Friday, and 100 for Saturday through Monday. Flux values and sunspots should rise again for a few days next week.
A coronal mass ejection near sunspot 588 spewed toward earth on April 6. Currently that sunspot is squarely in the center of the solar disk, aimed straight at us. The ejection should hit earth today (April 8). The predicted planetary A index for Thursday through Monday, April 8-12, is 30, 20, 15, 12 and 8.
There was a solar wind a couple of days back that caused geomagnetic instability late on April 5th and through most of April 6th. Another solar wind on April 3rd caused similar conditions.
For more information concerning propagation and an explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site at http://www.arrl.org/tis/info/propagation.html.
Sunspot numbers for April 1 through 7 were 100, 99, 68, 69, 85, 66 and 57 with a mean of 77.7. 10.7 cm flux was 112.8, 108.1, 107.4, 108.9, 108.7, 101.4 and 98.1, with a mean of 106.5. Estimated planetary A indices were 3, 3, 23, 12, 14, 21 and 10, with a mean of 12.3.