ZCZC AP20
QST de W1AW
Propagation Forecast Bulletin 20 ARLP020
From Tad Cook, K7VVV
Seattle, WA May 14, 1999
To all radio amateurs
SB PROP ARL ARLP020
ARLP020 Propagation de K7VVV
Solar flux and sunspot count took a big leap this week, with average sunspot numbers up nearly 64 points over last week, and average solar flux up over 35 points. Although last week's bulletin predicted solar flux drifting back below 130, this was based upon activity from about four weeks earlier rotating into view. There was no way to know in advance of the new sunspots which appeared this week.
The effect on HF propagation of solar flux near 180 on Sunday was dramatic. The author could hear renewed worldwide activity on 17 meters from his mobile rig, and could not help but wonder if cycle 23 was finally making its long awaited increase.
There was a coronal mass ejection on May 10, and the effects of this are now about to be felt. The predicted A index on Thursday is 20, but it should settle down to 12 and then 10 on Friday and Saturday. Solar flux on those days is predicted to be 150, 145 and 145. Flux values should bottom out around 125 on May 21 or 22, then rise again above 140 by May 27, reaching 170 again around June 5-7. Expect active geomagnetic conditions to return around May 25-28 due to recurring coronal holes.
Jim Secan (jim@nwra.com) of Northwest Research Associates (http://www.nwra.com) wrote wondering if any radio amateurs had noticed unusual HF propagation over the polar regions between 1200 and 2000z on May 11. He and Dave Evans of NASA (ddevans@mail.hq.nasa.gov) noticed that there was an unusual difference between southern and northern hemispheres in the extent of the auroral zone, which can be seen graphically at http://www.nwra.com/nwra/spawx/tiros.html. Although Dave noticed enhanced precipitation of energy in the northern polar cap region during this period, the high latitude K index was zero for most of the day.
In VHF news, N9BJG in Illinois heard the ZD8VHF 6 meter beacon from Ascension Island in the South Atlantic at 2020z on May 10, the first time since starting on VHF in 1976. Also on May 10 WB8XX in Ohio worked a number of South American stations on 6 meters.
Sunspot Numbers for May 6 through 12 were 141, 162, 192, 192, 174, 191 and 141 with a mean of 170.4. 10.7 cm flux was 146.9, 163.4, 171.9, 178.3, 169.5, 159.4 and 153.1, with a mean of 163.2, and estimated planetary A indices were 11, 9, 6, 6, 5, 5 and 9, with a mean of 7.3.
The path projection for this week is from New York.