ZCZC AP13
QST de W1AW
Propagation Forecast Bulletin 13 ARLP013
From Tad Cook, K7VVV
Seattle, WA March 28, 2002
To all radio amateurs
SB PROP ARL ARLP013
ARLP013 Propagation de K7VVV
This is coming out a day early because the ARRL is closed for the Good Friday holiday.
Average daily solar flux was down 10 points this week. Average sunspot numbers were up a bit, by 35 points. Sunday, March 24 was a very active geomagnetic day. Planetary A index was 47, with several periods of five and six K index, indicating a robust geomagnetic storm, the kind that causes dramatic auroral displays. The high latitude College A index, (from Fairbanks, Alaska) was 68, with K index at seven over two periods. Mid-latitude A index was 29. This activity was due to a coronal mass ejection on Saturday.
The outlook for the CQ Worldwide SSB WPX Contest this weekend is rather dicey, because there is the possibility of an eruption from sunspot 9878. The sunspot is earth-facing, and magnetic fields above this area have grown more complex recently. Next week earth will enter a solar wind stream from an unusual coronal hole. This coronal hole is odd because it has now appeared during four consecutive 27.5 day solar rotations. For the weekend, contesters will hope that any solar eruptions are later, rather than early. Because there is some delay (which can vary) with the different events that cause high geomagnetic activity, any solar activity this weekend might miss the contest.
Several readers requested path projections for the contest weekend, but it is far better if you download W6Elprop from http://www.qsl.net/w6elprop/ and do one for yourself. This way you can see it from your own station location, and look at paths projected toward anywhere. W6EL has a slightly new version 2.60 on his site. A good solar flux number to use is the current one averaged with the previous four or five days or so.
The latest projection as of Thursday had solar flux around 170 for Friday and Saturday, then flux below 170 until April 5-6. Geomagnetic conditions will probably be stable through the weekend, but become at least unsettled on Monday and Tuesday.
Sunspot numbers for March 21 through 27 were 160, 194, 176, 169, 162, 145 and 179 with a mean of 169.3. 10.7 cm flux was 174.1, 171.6, 170.4, 175.3, 170, 165.7 and 169.1, with a mean of 170.9, and estimated planetary A indices were 8, 8, 9, 47, 5, 11 and 5 with a mean of 13.3.