SB PROP @ ARL $ARLP016
ARLP016 Propagation de K7VVV
QST de W1AW
Propagation Forecast Bulletin 16 ARLP016
From Tad Cook, K7VVV
Seattle, WA April 21, 2000
To all radio amateurs
Sunspot numbers were up slightly this week, and average solar flux was down when compared to last week. Solar flux probably reached a short term low around Sunday or Monday, when the thrice daily readings for the two days were 157.9, 159, 156.7, 158.1, 157.9 and 157.1. Solar flux readings are taken daily at 1700, 2000 and 2300 UTC at Penticton, but it is the 2000 UTC reading that is the official solar flux value for the day. Sunday was the most disturbed day in terms of geomagnetic indices, when the planetary A index was 23 and the K index went as high as five.
Solar flux should rise over the next few days, going above 200 around April 24 and peaking near 220 around April 28 or 29. This should improve 10 and 12 meters, although the seasonal effects as we move toward late spring and summer will mean that the highest HF bands are not as interesting as they were at the equinox.
The forecast for the next five days, Friday through Tuesday, shows solar flux values of 185. 190, 195, 200 and 210. Predicted planetary A index for those same days is 12, 5, 5, 5, and 8. Geomagnetic conditions should stay fairly quiet, but April 29 could have unsettled to active geomagnetic conditions.
An AP wire service story this week talked about research reported in the May 1 issue of Geophysical Research Letters which uses data from the SOHO satellite to determine when solar activity on the other side of the sun may rotate into view. An increase in L-Alpha radiation accompanies sunspots, and it brightens hydrogen atoms in space. The SOHO satellite can detect these hydrogen atoms that are illuminated by sunspots from areas of the sun not currently facing earth, and researchers can predict when these active areas will rotate into view.
Sunspot numbers for April 13 through 19 were 190, 173, 177, 170, 166, 167 and 179 with a mean of 174.6. 10.7 cm flux was 164, 165.2, 163.7, 159, 157.9, 160.4 and 167.7, with a mean of 162.6, and estimated planetary A indices were 8, 5, 7, 23, 14, 7 and 12, with a mean of 10.9.
Path projections for this weekend are from Miami, Florida.