QST de W1AW
Propagation Forecast Bulletin 8 ARLP008
From Tad Cook, K7VVV
Seattle, WA February 25, 2000
To all radio amateurs
SB PROP ARL ARLP008
ARLP008 Propagation de K7VVV
Solar flux and sunspot activity were down last week, but heading back up. Average solar flux for last week compared to the previous week was down almost 4 points, and sunspot numbers were off about 28 points. The low point was Friday, February 18, when the three solar flux measurements for the day were 139.6, 141.1 and 140.4. The noon measurement of 141.1 is the official reading for the day. Solar flux is expected to rise, with the projection for Friday through Tuesday of 197, 197, 200, 200 and 204. Solar flux for the near term is expected to peak around 205 on Wednesday or Thursday, March 1 and 2, then decline to below 170 by March 9, and bottom out near 130 around March 23 or 24.
Planetary A index has been rising, due to a well-placed coronal hole streaming charged particles toward the earth. NASA has an interesting article about this as well as a dramatic photo online at http://www.spacescience.com/headlines/y2000/ast23feb_2.htm. Also check http://www.spaceweather.com, which on Thursday had an article about a gust of solar wind at 1430z on February 24.
The projected planetary A index for Friday through Tuesday is 20, 18, 15, 13 and 10. Conditions may be disturbed again around March 4 and 5, and fairly quiet between March 13-20. Based on the current solar rotation, disturbed conditions may recur around March 22-23, and possibly quiet conditions again around March 26-29, although predictions that far in the future are more of a guess. These projections are based upon sunspots and coronal holes moving across the visible solar surface, as the sun rotates relative to earth every 27.5 days. Various features grow and fade with time, and new areas appear. Some are oriented toward earth and have a large effect, while others do not.
The coronal hole that is causing the current geomagnetic disturbance has been visible for the last seven solar rotations.
Doug Brandon, N6RT wrote to ask about the URL for Cary Oler's Solar Terrestrial Dispatch web site, which seemed to disappear some time back. Doug did some detective work, and found that it had moved. The new site is at http://solar.spacew.com/.
George Jacobs, W3ASK has an interesting item in his propagation column in the March issue of CQ Magazine concerning equinoctial propagation. This is about the effect that occurs in spring and fall seasons when the daylight distributed between the northern and southern hemisphere is roughly equal, dependent on how close the date is to the equinox. He says that during March intercontinental openings on 160-30 meters should peak just before local sunrise and again at local sunset. 20 meter openings should peak an hour or two after sunrise and again for an hour or so after sunset. 17-6 meter intercontinental openings should peak during daylight hours. Signals on these upper bands are stronger toward the west around and after sunset, while toward the east they are stronger before noon. He notes that signals to the south are stronger after sunrise and again late in the afternoon. W3ASK has a web site at http://www.gjainc.com/.
Sunspot numbers for February 17 through 23 were 152, 146, 126, 131, 122, 129 and 155 with a mean of 137.3. 10.7 cm flux was 168.4 141.1, 144.8, 153.3, 152.1, 172.3 and 185.1, with a mean of 159.6, and estimated planetary A indices were 6, 2, 4, 5, 15, 5 and 9, with a mean of 6.6.
Path projections this week are from Boston, MA, and are based on Sunday, February 27 with a solar flux of 200.