QST de W1AW
Propagation Forecast Bulletin 6 ARLP006
From Tad Cook, K7VVV
Seattle, WA February 8, 2002
To all radio amateurs
SB PROP ARL ARLP006
ARLP006 Propagation de K7VVV
Average daily sunspot numbers were higher, rising 38 points over the previous week. Solar flux continued a decline from last week, with average daily flux down over 18 points. Solar flux for the short term peaked January 29, and has declined since. Predicted solar flux for Friday through Monday is 190, 185, 180 and 175. Flux values should reach a minimum near 170 for the short term, then jump suddenly higher around February 16. Geomagnetic conditions are expected to be moderate.
For the past few days the earth has been in a stream of solar wind from a coronal hole, causing some geomagnetic activity. Planetary K indices were as high as 4. Also on February 1 there was another solar wind disturbance commencing around 0558z which caused some aurora activity and planetary K indices as high as 5. This is generally bad for HF communications because of absorption, especially over polar paths. What HF operators generally want to see are many sunspots, such as we have currently at the peak of this solar cycle, but without flares or the accompanying geomagnetic effects.
Every day we receive email asking for explanations of the indices in this bulletin and requests for basic texts. The New Shortwave Propagation Handbook published by CQ is a good source, and also the propagation section of any recent ARRL Handbook is useful. You can also find an archive of back issues of this bulletin at http://www.arrl.org/w1aw/prop/ . A good explanation for the numbers in this bulletin by K9LA was in the first bulletin of this New Year, Propagation Forecast Bulletin ARLP001 in that same archive. Other issues of the bulletin will cover propagation topics of interest to hams.
Sunspot numbers for January 31 through February 6 were 238, 256, 222, 273, 274, 286 and 226 with a mean of 253.6. 10.7 cm flux was 242.6, 245.6, 240.6, 232.9, 234.6, 220.6 and 202.5, with a mean of 231.3, and estimated planetary A indices were 5, 11, 18, 5, 6, 16 and 16 with a mean of 11.