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.

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