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ARRL Propagation Bulletin ARLP016 (2004)

ARLP016 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 16  ARLP016
From Tad Cook, K7RA
Seattle, WA  April 16, 2004
To all radio amateurs 

ARLP016 Propagation de K7RA

Geomagnetic activity was pleasantly quiet this week, but sunspot and
solar flux numbers were way down. Average daily sunspot numbers for
the week were down over 44 points to 33.4, and solar flux was down
15 points to 91.5. Spring is a nice time of year for HF propagation,
except that activity this low will reduce openings on 15, 12 and 10

Currently sunspot 591 is rotating away from earth while 592 and 594
are coming into full view. However, these are not large spots.
Solar flux is expected to rise above 100 this weekend, April 17-18,
and reach a peak around 120 on or near April 24. There is a small
possibility of a coronal mass ejection from 591 today.

On April 8 and 10 energy from a couple of coronal mass ejections hit
earth, but both were tame. They were enough to cause a rise in
geo-activity near Polar Regions. Alaska's college A index at
Fairbanks rose to 30 on April 8, but the mid-latitude and planetary
A index were just 16.

The ARRL Technical Information Service (TIS) has a resource page
devoted to propagation. Within the next few weeks I hope to get a
couple of new items written by Carl Luetzelschwab, K9LA, concerning
propagation prediction software posted there. These are short
practical pieces about two free programs, VOACAP, and the W6ELprop
software. The W6EL program is the one used for making the occasional
path predictions in this bulletin.

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the TIS Propagation page on
the ARRL Web site at,

Sunspot numbers for April 8 through 14 were 33, 18, 20, 16, 37, 41
and 69 with a mean of 33.4. 10.7 cm flux was 93.5, 90, 87.7, 89.6,
91.3, 93.1 and 95.2, with a mean of 91.5. Estimated planetary A
indices were 16, 16, 10, 8, 11, 6 and 5, with a mean of 10.3.


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