ARRL

ARRL Propagation Bulletin ARLP003 (2001)

SB PROP @ ARL $ARLP003
ARLP003 Propagation de K7VVV

ZCZC AP03
QST de W1AW  
Propagation Forecast Bulletin 3  ARLP003
From Tad Cook, K7VVV
Seattle, WA  January 19, 2001
To all radio amateurs 

SB PROP ARL ARLP003
ARLP003 Propagation de K7VVV

Average solar flux dropped a little over 2 points and average
sunspot numbers declined 22 points over the past week.  On Wednesday
the sunspot number dropped below 100 for the first time since
December 12.  The outlook for the near term is for continued low
activity.

Last week's bulletin mentioned a short term solar flux peak around
200 on January 17, but instead it was only 151.9.  The largest
sunspot group is rotating out of view around the sun's western limb,
and the near term outlook is for solar flux to continue declining
for the next few days, to a minimum of 140 on January 21, then rise
to 170 on January 25, and stay around 175 from January 26 through
February 1, peaking at 180 on February 2 or 3.

These numbers are far below recent values over 200, and are another
sign that we have passed the peak of the solar cycle.  But along
with this decline in activity come stable geomagnetic conditions, as
the chance for solar flares declines along with the sunspot
activity.  Planetary A indices are expected to remain in the single
digits until the end of this month.  With the longer winter nights,
this looks good for DX on 160, 80 and 40 meters.

Not only are we experiencing stable geomagnetic conditions, but in
the northern hemisphere, atmospheric noise is also at a seasonal
low.  The higher frequency bands (20 meters and above) are still
good during the day, but because of the season 20 meters is not open
late into the evening as it was in the fall.  Of course, the
southern hemisphere is experiencing summer right now.

On Saturday earth is expected to move through a solar wind coming
from a small coronal hole, but currently no geomagnetic disturbance
is predicted.

Sunspot numbers for January 11 through 17 were 173, 173, 146, 181,
154, 115 and 71 with a mean of 144.7. 10.7 cm flux was 165.9, 178.3,
184.3, 176.3, 169.2, 161.9 and 151.9, with a mean of 169.7, and
estimated planetary A indices were 5, 7, 5, 8, 7, 6 and 7 with a
mean of 6.4.
NNNN
/EX