ARRL

ARRL Propagation Bulletin ARLP044 (2001)

SB PROP @ ARL $ARLP044
ARLP044 Propagation de K7VVV

ZCZC AP44
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.
NNNN
/EX