The
K7VVV Solar Update
SEATTLE, WA, May 3, 2002--Both average solar flux and daily
sunspot numbers dropped last week. Sunspot numbers were down more than 30
points, and solar flux was down nearly 20 points. 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. Based on 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,
resulting in 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. Ten 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. 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. There also are many very old
drawings, including sets from the years 1128 to 1800.
Next
week K9LA takes over the bulletin while K7VVV is out of town.
Sunspot
numbers for April 25 through May 1 were 208, 160, 173, 121, 124, 113 and 166,
with a mean of 152.1. The 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. Estimated planetary A indices were 5, 6,
8, 19, 9, 8 and 5 with a mean of 8.6.
Amateur
solar observer Tad Cook, K7VVV Seattle, Washington, provides this weekly report
on solar conditions and propagation. This report also is available via W1AW
every Friday, and an abbreviated version also appears in The ARRL Letter.
Readers may contact the author via k7vvv@arrl.net.
Page last modified: 11:33 AM, 03 May 2002 ET
Page author: awextra@arrl.org
Copyright © 2002, American Radio Relay League, Inc. All Rights Reserved.
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