ZCZC AP08
QST de W1AW
Propagation Forecast Bulletin 8 ARLP007
From Tad Cook, K7VVV
Seattle, WA February 19, 1999
To all radio amateurs
SB PROP ARL ARLP008
ARLP008 Propagation de K7VVV
Solar activity took a great leap forward this week. The solar flux on Sunday was 204.6, which is the highest it has been since April 19, 1992, when it was 205.7. The Sunday sunspot number of 211 was the highest since July 12, 1992, when it was 215. Both of these earlier readings were from the down side of the previous solar cycle.
Average solar flux for the week was up nearly 72 points compared to last week, and average sunspot numbers increased by almost 120. As a result of higher solar activity, conditions on the higher end of the HF spectrum are much improved.
A major geomagnetic storm commenced at 0250z on February 18, and the resulting planetary A index for the day was 54. The high latitude A index was 89, and the associated K indices went as high as 8, which is extremely disturbed. The should result in auroral displays. The predicted A index for Friday is 30, for Saturday is 15, and Sunday is 10. This does not bode well for the ARRL International CW DX Contest this weekend, although by Sunday conditions will probably have recovered.
A look at recent solar images shows quite a few pox on old sol. Check out some recent solar images on the web in the archive at http://www.sec.noaa.gov/solar_images/ImageIndex.cgi, and then click on any small image to make it larger. For a more dramatic presentation, see the animated solar rotation at http://spaceweather.com/java/solar-anim.html.
For Friday through Sunday, look for solar flux values of 160, 155 and 150. Expect the solar flux to continue down to around 135 on Monday, 125 on Tuesday, then below 120 around February 27, 110 around March 1 and 2, and bottoming out for the short term at 105 from March 3-5. Based on the current 27.5 day solar rotation, solar flux should rise again, going above 150 after March 9, 170 after March 11, and hit below 200 before mid-month. Unsettled to active geomagnetic conditions are forecast for March 10-12.
In VHF news, WP4O in Puerto Rico worked Argentina on 6 meter SSB just after 2100z on Tuesday. He reported that the opening lasted only about three minutes.
W0LQV kindly pointed out an error in the January 29 solar flux reported in ARLP006. Instead of 177.7 it should have been 117.7, which made the average solar flux for the week 115.3 instead of 123.9. Those who keep track of the data in these bulletins will want to change their records.
Several people wrote to point out that the author's email address reported in last week's bulletin should end in net instead of org. The correct email address is k7vvv@arrl.net, or you can use tad@ssc.com.
Sunspot Numbers for February 11 through 17 were 84, 165, 199, 211, 167, 176 and 135 with a mean of 162.4. 10.7 cm flux was 163.5, 188.4, 198.4, 204.6, 190.1, 191.8 and 189.8, with a mean of 189.5, and estimated planetary A indices were 16, 21, 7, 9, 13, 4 and 16, with a mean of 12.3.