ARRL

ARRL Propagation Bulletin ARLP003 (2004)

SB PROP @ ARL $ARLP003
ARLP003 Propagation de K7RA

ZCZC AP03
QST de W1AW  
Propagation Forecast Bulletin 3  ARLP003
From Tad Cook, K7RA
Seattle, WA  January 16, 2004
To all radio amateurs 

SB PROP ARL ARLP003
ARLP003 Propagation de K7RA

Both average daily sunspot numbers and solar flux were up just a few
points this week over last. The average daily planetary A index, a
measure of geomagnetic stability, dropped from 23.4 to 15.9. HF
radio operators prefer conditions when the A index is low and the
solar flux and sunspot numbers are high.

Solar flux has been around 118-120, but is expected to rise over the
next few days. Solar flux for Friday through Sunday, January 16-18
is predicted at 125, 130 and 135. Solar flux values should peak
around 140 from January 19-21 before dropping back.

As expected during the solar cycle decline, sunspot counts have been
low. When this bulletin was written, there were only two sunspot
groups visible, and helioseismic imaging showed only a small sunspot
group on the sun's far side. When the daily sunspot number reached
118 on January 8, it was the first time the number rose above 100
since December 23, and it hasn't been above 100 since.

Earth is moving into a solar wind stream from a coronal hole, and
geomagnetic conditions could become active. The predicted planetary
A index for January 16-19 is 18, 25, 18 and 15. Conditions on
Saturday may be similar to January 10, except the day will be
slightly longer (7 minutes longer in Dallas, for instance, and 13
minutes longer in Seattle) and the solar flux and sunspot count
should be slightly higher.

Here is a link we haven't referenced in some time. Look at the Solar
Terrestrial Dispatch at http://www.spacew.com/ . Note the Ham Radio
link on the left and the various resources there, such as MUF maps.
Another interesting link is to Michigan Tech's site devoted to
auroras at http://www.geo.mtu.edu/weather/aurora/ .

A new service used by the author is Spaceweather Phone. Unlike all
other resources referenced in this bulletin, this one is not free.
Subscribers can set thresholds for various events such as
geomagnetic planetary K index above a certain value, or X class
solar flares, just to name two. Once the customized threshold is
passed, Spaceweather Phone automatically calls you and delivers a
message about the event in progress. See it at
http://spaceweatherphone.com/ .

For more information about propagation and an explanation of the
numbers used in this bulletin see the Propagation page on the ARRL
Web site at http://www.arrl.org/tis/info/propagation.html .

Sunspot numbers for January 8 through 14 were 118, 88, 66, 53, 77,
53 and 58 with a mean of 73.3. 10.7 cm flux was 120.1, 118.4, 119.2,
118.5, 118.3, 117.9 and 121.1, with a mean of 119.1. Estimated
planetary A indices were 9, 21, 24, 17, 10, 18 and 12, with a mean
of 15.9.
NNNN
/EX