ZCZC AP17
QST de W1AW
Propagation Forecast Bulletin 17 ARLP017
From Tad Cook, K7VVV
Seattle, WA April 23, 1999
To all radio amateurs
SB PROP ARL ARLP017
ARLP017 Propagation de K7VVV
This was another down week for sunspots and solar flux, although with the flares and associated geomagnetic activity, we can't say that solar activity was down. On Saturday the planetary A index reached 47 with the K index as high as 7, an indication of a severe geomagnetic storm. This was caused by a coronal mass ejection, another name for a solar flare. Conditions were again unsettled to minor storm a few days later when the planetary A index was 21.
K0XY wrote to complain about the solar flux, and with all of the recent mail expressing fear that this cycle has already peaked, I decided to check with a forecaster at the NOAH Space Environment Center in Colorado. They are still sticking with their forecast made last year, that the peak of cycle 23 is probably a year from now, or perhaps it will peak at the end of 2000. It is important to keep in mind that when looking at past solar cycles, we are often observing smoothed numbers, and in fact there are often periods before a cycle reaches a peak when there will be a lull in activity. There is also a possibility that this cycle could be like cycle 22, which had a broad double peak.
It should be noted that while radio amateurs often hope for high solar activity, most of the individuals and organizations contacting the Space Environment Center with concerns about solar activity do not. These are the folks who are working with satellites, power distribution systems and pipelines, and worry about the sun bombarding the earth with energy during high flare activity.
Look for a flat solar flux this week, with the numbers remaining around 105. The planetary A index for the weekend, Friday through Sunday, should be 7, 7 and 10. Don't expect the solar flux to increase until after the end of April, with 130 by May 2, 140 by May 4, but then drifting back to 120 by May 12. Of course, as always, these projections are only based upon activity seen during the last rotation of the sun, so new sunspots could appear and liven things up.
Sunspot Numbers for April 15 through 21 were 95, 87, 99, 98, 90, 79 and 79 with a mean of 89.6. 10.7 cm flux was 121.8, 122.9, 115.7, 112.8, 110, 104.8 and 103.4, with a mean of 113.1, and estimated planetary A indices were 4, 14, 47, 6, 13, 21 and 12, with a mean of 16.7.
The path projection for this week is from Alaska, somewhere between Anchorage and Fairbanks: