QST de W1AW
Propagation Forecast Bulletin 41 ARLP041
From Tad Cook, K7VVV
Seattle, WA October 8, 1999
To all radio amateurs
SB PROP ARL ARLP041
ARLP041 Propagation de K7VVV
Solar flux and sunspot numbers were up this week, with sunspot numbers almost double the week previous, but average solar flux up less than six points. Recent geomagnetic instability finally quieted down, and on Wednesday morning UTC (Tuesday night in North America) the K index at both the mid latitudes and the College Index from Alaska were both zero.
Solar flux has been falling the past few days, after peaking at 146.2 on Tuesday. The official daily numbers are always from the 2000 UTC reading at Penticton, British Columbia, but there are readings at 1700 and 2300 UTC as well. Following the 2000 UTC reading on Tuesday, the flux for each of the three daily readings, through 2000 UTC Thursday were 146.7, 139.6, 133.6, 132.1, 131.7, and 129.4.
The projected flux values for the next seven days, Friday through Thursday, October 14 are 130, 135, 140, 145, 145, 150, and 150. The projected A indices for the same dates are 10, 15, 25, 30, 20, 15 and 15. Monday, October 11 looks like an unstable geomagnetic day. October 24 could be a bad day as well.
W7AFC wrote to ask for an explanation of the various numbers presented in this bulletin. The last time this bulletin had a detailed explanation of the meaning of the numbers was ARLP030. You can see it at http://www.arrl.org/w1aw/prop/1999-arlp030.html on the ARRL web site.
The path projections are intended to show the times when the bands are most likely to be open to the target areas from the point of origin, which changes every week. There may be openings at other times, but the periods shown are a very good bet for a strong opening.
Sunspot numbers for September 30 through October 6 were 84, 67, 47, 117, 148, 160 and 176 with a mean of 114.1. 10.7 cm flux was 124.8, 121.6, 126.3, 134.5, 144.4, 146.2 and 133.6, with a mean of 133.1, and estimated planetary A indices were 29, 11, 15, 10, 15, 16 and 6, with a mean of 14.6.
The path projection for this weekend is from Billings, Montana.