ARRL Propagation Bulletin ARLP018 (2002)

ARLP018 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 18  ARLP018
From Tad Cook, K7VVV
Seattle, WA  May 3, 2002
To all radio amateurs 

ARLP018 Propagation de K7VVV

Both average solar flux and daily sunspot numbers dropped last week.
Sunspot numbers were down over 30 points, and solar flux was down
nearly 20 points. But now that April is over, let's look at monthly
averages. Average sunspot numbers for October through April were
197.4, 178.6, 217.5, 189, 194.5, 153.1 and 194.9. Average solar flux
values for the same seven months were 208.1, 212.7, 236.5, 227.3,
205, 179.5 and 189.8. From these numbers it is apparent that April
had higher solar flux and sunspot counts than March, but it is down
from previous months.

During the last half of April, three coronal mass ejections sent
energy past earth, and the results were geomagnetic storms around
April 17-20 and April 23. Energy from a coronal hole should sweep
past us shortly, but it shouldn't cause the kind of upset that
April's storms brought us.

Over the next few days expect moderate geomagnetic activity with a
rising solar flux. Flux values are expected to rise above 180 by
Sunday, and peak for the near term above 200 around one week from

Lower geomagnetic indices are generally good for HF propagation. The
solar flux is rising, which is also good. 10-meters should be fading
away as we move toward summer, but 15-meters should do quite well
over the next month. This summer 20-meters should be excellent
during nighttime.

WB6RIB sent along a URL for a fascinating web site devoted to the
50-foot solar tower at the Mount Wilson Observatory in California.
You can point your web browser toward to see this. To me the
most interesting feature of this site is the archive of hand-drawn
pencil sketches of the sun's surface dating back to January 4, 1917.

The story of these drawings (which are really tracings) and how they
are made may be seen at There are many very
old drawings, including sets from the years 1128 to 1800.

Next week Carl, K9LA takes over the bulletin while K7VVV leaves

Sunspot numbers for April 25 through May 1 were 208, 160, 173, 121,
124, 113 and 166 with a mean of 152.1. 10.7 cm flux was 167.3,
162.6, 156.9, 147.1, 153, 153.4 and 162.4, with a mean of 157.5, and
estimated planetary A indices were 5, 6, 8, 19, 9, 8 and 5 with a
mean of 8.6.