ZCZC AP19
QST de W1AW
Propagation Forecast Bulletin 19 ARLP019
From Tad Cook, K7VVV
Seattle, WA May 4, 2001
To all radio amateurs
SB PROP ARL ARLP019
ARLP019 Propagation de K7VVV
The report this week will be a little slim due to computer problems at K7VVV. For anyone sending email, your mail should be answered by early next week. K7VVV@arrl.net is still a good address.
Sunspot activity and solar flux were both up, with average sunspot numbers for the week increasing by 30 points and average solar flux up by almost 7 points. Solar flux peaked on Tuesday at 209.7. Saturday was the most disturbed day, with the planetary A index at 28, and the Fairbanks, Alaska high-latitude College A index at 46.
This was from an interplanetary shock wave produced by a flare on April 26. The energy from this flare was expected to arrive Sunday, but showed up a day earlier. The peak in solar flux, last week expected to be on the weekend, arrived two or three days later than expected.
Currently the solar disk is covered with sunspots, although they are small, fairly non-complex regions, not like the recent sunspot 9393 which caused so much excitement over the previous two solar rotations. There is some possibility of flare activity from sunspot 9445, which exhibits a complex magnetic field.
The latest forecast shows solar flux declining over the next few days, 170 on Friday, 165 on Saturday, 160 on Sunday and 155 on Monday. Flux is expected to reach a short term minimum around 130 between May 13-15, then peak again from May 20-29. The next peak is expected to be lower than recent activity, and not reach a flux value of 200. This is assuming that no new large sunspot regions emerge, which we really have no way of knowing. Geomagnetic indices should be unsettled to active this weekend, with a planetary A index of 15 on Friday and Saturday, 12 on Sunday and 10 on Monday.
Sunspot numbers for April 26 through May 2 were 193, 181, 173, 161, 178, 152 and 179 with a mean of 173.9. 10.7 cm flux was 196.2, 190.8, 187.8, 191.7, 187.8, 209.7 and 176.2, with a mean of 191.5, and estimated planetary A indices were 7, 6, 28, 15, 5, 4 and 6 with a mean of 10.1.