ZCZC AP40
QST de W1AW
Propagation Forecast Bulletin 40 ARLP040
From Tad Cook, K7VVV
Seattle, WA October 3, 1997
To all radio amateurs
SB PROP ARL ARLP040
ARLP040 Propagation de K7VVV
Again this week the average solar flux for the previous 90 days rose two points, and again the daily flux values were above 83, which was the high average value on Wednesday, the last day of the reporting week. Wednesday was the fifty eighty consecutive day that the solar flux was above the average for the preceding 90 days, and this is a very positive sign indicating a general upward trend in the new solar cycle.
This increased activity can have a downside though, and on Wednesday the geomagnetic field was very unstable, which generally means higher absorption, especially on high latitude and polar signal paths. The planetary A index was 41, and planetary K index went as high as 6. The A index measured at College, Alaska was 67, and the highest K index was 8, which means miserable HF conditions. These stormy conditions were caused by a flare and a coronal mass ejection a few days earlier. For a good explanation of K and A indices, see the chapter on propagation in any recent edition of the ARRL Handbook.
Conditions stabilized the next day, and geomagnetic conditions were very stable, with the Alaska K indices at zero over most of the day, and worldwide it was mostly one and zero.
Over the next few days look for higher solar activity, with the solar flux up over 100 around October 7 to 11. It may dip below 90 after mid month, then rise again to around 90 until November. Based on the previous solar rotation, October 25 and 26 may be unstable. Look for a smaller possibility of geomagnetic instability on October 12 and again on October 15.
Sunspot Numbers for September 25 through October 1 were 50, 40, 33, 23, 27, 25 and 38 with a mean of 33.7. 10.7 cm flux was 88.5, 89.1, 88.4, 87.2, 89.7, 87.7 and 87.1, with a mean of 88.2, and estimated planetary A indices were 3, 4, 13, 14, 9, 7, and 41, with a mean of 13.
For the VK/ZL/Oceania contest this weekend, here are a few projections for conditions to that part of the world.
From the center of the continental United States check 80 meters 0630 to 1230z, 40 meters 0600 to 1300z, 20 meters 0300 to 1530z, 15 meters 1930 to 0130z, and 10 meters 2130 to 2330z.
From Southern California, check 80 meters 0630 to 1400z, 40 meters 0600 to 1430z, 20 meters 0300 to 1030z, 15 meters 1900 to 0330z, and 10 meters 2300 to 0130z.
From Texas check 80 meters 0630 to 1230z, 40 meters 0600 to 1300z, 20 meters 0230 to 1100z, 15 meters 1830 to 0200z and 10 meters 2130 to 0030z.
From the Southeast states check 80 meters 0700 to 1200z, 40 meters 0600 to 1230z, 20 meters around 0300z and 1300 to 1500z, 15 meters with weaker signals around 1900 to 2300z, and possible 10 meter openings around 2130 to 2300z.
From the New York area check 80 meters 0700 to 1130z, 40 meters 0630 to 1200z, 20 meters possibly around 0400 to 0530z and 1300 to 1530z, although conditions do not look promising, and 15 meters with only fair signals from 1930 to 2330z, and a possible opening on 10 meters from 2000 to 2130z.