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.