ZCZC AP37
QST de W1AW
Propagation Forecast Bulletin 37 ARLP037
From Tad Cook, K7VVV
Seattle, WA September 12, 1997
To all radio amateurs
SB PROP ARL ARLP037
ARLP037 Propagation de K7VVV
The rise in solar activity continues, and this past week on Monday solar flux values peaked at 119.4. The last time the solar flux was above this value was January 27, 1994. On the same Monday the sunspot number was 101, which has been unequaled since September 3, 1994. We are definitely through the minimum and on the upswing of the next solar cycle.
The average solar flux for the previous 90 days rose another two points this past week (to 77), as it had the previous week. September 11 was the 38th consecutive day that the flux was above the 90 day average. Along with this greatly increased activity has been some geomagnetic disturbances. The most disturbed period over this past week was around 0600 to 0900 UTC on September 9.
Recent projections from the NOAA Space Environment Service Center show the solar flux dropping below 100 after September 17, then back above 100 around September 26, and above 115 after October 4. These estimates are based upon the previous solar rotation, so new active regions on the Sun could send these numbers higher. This new activity means that long distance propagation is now possible on the upper HF bands, where prior to this 20 meters was the primary band for worldwide propagation.
Check 15 and even 10 meters, where openings are now possible, especially over north to south paths. Combined with the progression toward the Fall equinox, conditions now and over the next month should be the best seen in several years.
Sunspot Numbers for September 4 through 10 were 56, 79, 85, 84, 97, 101 and 95 with a mean of 85.3. 10.7 cm flux was 93, 96, 97.6, 102, 119.4, 116.1 and 114.9, with a mean of 105.6, and estimated planetary A indices were 19, 5, 7, 3, 9, 19, and 19, with a mean of 11.6.