ZCZC AP25
QST de W1AW
Propagation Forecast Bulletin 25 ARLP025
From Tad Cook, K7RA
Seattle, WA June 18, 2004
To all radio amateurs
SB PROP ARL ARLP025
ARLP025 Propagation de K7RA
Several large sunspot groups now pepper the earth-facing side of the sun, and sunspots are also detected on the sun's far side. Daily sunspot numbers rose this week to a high of 113, although the weekly average was down a few points from last week. Average daily solar flux numbers rose this week over eight points. Geomagnetic conditions were fairly quiet, with the most active day on Tuesday, June 15.
The current forecast shows solar flux up around 110 over the weekend, June 18-20, then dropping to 100 by June 25. Conditions don't look bad for this weekend's All Asian DX CW Contest.
As the current solar cycle slowly declines, it is interesting to anticipate how long it might be past the solar minimum for sunspot activity to rise again to current levels. A prediction from NOAA, seen at http://sec.noaa.gov/ftpdir/weekly/Predict.txt shows the solar minimum around December 2006. The furthest out the chart projects is December 2007, with a predicted sunspot number around 21.3. The same chart predicts a level near that value around December 2004. This means that after December 2004, conditions won't rise again to that level until three years later.
To look at historical charts of previous solar cycles, check http://www.qsl.net/w3df/sfarch.html and http://www.wm7d.net/hamradio/solar/historical.shtml.
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service propagation page at http://www.arrl.org/tis/info/propagation.html.
Sunspot numbers for June 10 through 16 were 50, 45, 28, 55, 77, 87 and 113 with a mean of 65. 10.7 cm flux was 82.5, 83.9, 88, 95.2, 99.9, 109.4 and 111.5, with a mean of 95.8. Estimated planetary A indices were 11, 10, 7, 4, 11, 16 and 7, with a mean of 9.4. Estimated mid-latitude A indices were 8, 5, 5, 3, 9, 14 and 7, with a mean of 7.3.