[LeArc] Propagation Forecast Bulletin 18 ARLP018

[Joseph L. Rossmiller]

SB PROP @ ARL $ARLP018
ARLP018 Propagation de K7VVV

ZCZC AP18
QST de W1AW
Propagation Forecast Bulletin 18  ARLP018
>From Tad Cook, K7VVV
Seattle, WA  May 3, 2002
To all radio amateurs

SB PROP ARL ARLP018
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 now.

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
http://www.astro.ucla.edu/~obs/intro.html 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 http://www.astro.ucla.edu/~obs/150_draw.html. 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 town.

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.

NNNN
/EX