QST de W1AW
Propagation Forecast Bulletin 44 ARLP044
From Tad Cook, K7VVV
Seattle, WA October 26, 2001
To all radio amateurs
SB PROP ARL ARLP044
ARLP044 Propagation de K7VVV
Solar flux and sunspot numbers rose this week. Unfortunately for HF operators, so did geomagnetic activity. Average sunspot numbers rose nearly 47 points and average daily solar flux was up nearly 43 points.
Geomagnetic conditions were quite active on Sunday and Monday, and reached a peak on Monday with a planetary A index of 66. Planetary K indices were 5 during three of the three-hour reporting periods, 6 during three periods, and 7 during one period. This indicates a severe geomagnetic storm, one that produced dramatic aurora displays.
Conditions were worse toward the poles. Alaska's College A index was 93 on Monday, with the K index as high as 8. HF radio operators like a K index of 3 or less.
What is bad for HF conditions can make VHF very interesting. JA7SSB reported that 6-meters was quite active in Japan, with SSB signals from Italy monitored in Sendai City, 350 km north of Tokyo around 0600z on Monday. On both Monday and Tuesday from 0600-0900z, JA7SSB was hearing VK9 (Norfolk Island), VK, A51, KH6 and FO signals from his QTH in Fukushima, 80 km south of Sendai.
All this excitement was from solar activity on Friday when flares erupted above sunspot 9661. Another coronal mass ejection hit the earth's magnetosphere on October 25, but did not cause a disturbance. K indices on Wednesday and Thursday were very low, around 1 and 2, and the planetary A index on Wednesday 3.
Even though conditions had quieted down by Thursday, this does not look like a quiet weekend for the CQ Worldwide DX SSB Contest. A flare around 1500z on Thursday caused a strong radio blackout across the Americas and Europe. This expanding cloud of energy will probably strike earth this weekend, ruining northern propagation paths.
When this occurs, some operators notice an enhanced north-south propagation path, but what really happens is that the north-south path is often the only remaining path for HF propagation.
The latest projections late Thursday predict a declining solar flux of 230, 225, 220 and 215 for Friday through Monday, and an A index of 10, 20, 30 and 15 for those same days.
Sunspot numbers for October 18 through 24 were 182, 219, 230, 239, 207, 231 and 230 with a mean of 219.7. 10.7 cm flux was 228.7, 247.6, 244.7, 224.1, 232.7, 226.4 and 238.7, with a mean of 234.7, and estimated planetary A indices were 4, 8, 10, 40, 66, 15 and 3 with a mean of 20.9.