QST de W1AW
Propagation Forecast Bulletin 16 ARLP016
>From Tad Cook, K7RA
Seattle, WA April 22, 2005
To all radio amateurs
SB PROP ARL ARLP016
ARLP016 Propagation de K7RA
Little changed in sunspots and solar flux this week, but it was one
of those periods were average daily sunspot numbers were up
slightly, and average daily solar flux was down a little. Average
daily sunspot numbers were up over ten points to 50.9, and average
daily solar flux was down five points to 81.9.
Geomagnetic conditions were calmer and quieter, with no really
stormy days at all. The most unsettled days saw planetary A index
of 19 for April 14, while the mid-latitude A index was 14. On April
20 the planetary A index was 21 and the mid-latitude A index was 12.
No large sunspots are detected on the sun's far side, and the
projection for the next week is for more of the same in terms of
solar flux and sunspot numbers. April 25-28 could see a slight rise
in sunspot count. April 22-23 could produce some unsettled
geomagnetic conditions if the interplanetary magnetic field turns
south. Currently as this bulletin is written early Friday, the
field points north, tending to deflect any solar wind. While there
isn't much in the way of sunspots, at least conditions are quiet and
there is more sunlight for those of us in the Northern Hemisphere.
Randy Crews, W7TJ of Spokane, Washington sent a note in response to
last week's bulletin mentioning 160 meter propagation. He writes,
''Here is one of the best articles on 160M Propagation I have read.''
The article appeared in CQ Magazine in 1998. Read it at
solar.spacew.com/cq/cqmar98.pdf. Thanks to Randy for sharing
it with us.
If you would like to comment or have a tip, email the author at,
For more information concerning radio propagation and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at,
www.arrl.org/tis/info/propagation.html. An archive of past
bulletins is found at www.arrl.org/w1aw/prop/.
Sunspot numbers for April 14 through 20 were 63, 61, 52, 54, 44, 43
and 39 with a mean of 50.9. 10.7 cm flux was 85.4, 84.9, 82.9, 83.6,
81.3, 78.2 and 77, with a mean of 81.9. Estimated planetary A
indices were 19, 13, 7, 5, 8, 8 and 21 with a mean of 11.6.
Estimated mid-latitude A indices were 14, 7, 4, 4, 5, 6 and 12, with
a mean of 7.4.
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