The K7RA Solar Update

SEATTLE, WA, Nov 29, 2004--Because last week's "Solar Update" was prepared Tuesday, November 23, it didn't include the weekly "numbers" at the end. This bonus bulletin will get us caught up. Our normal reporting week runs from Thursday through Wednesday, so we are reporting and comparing data from November 18 to 24 with the earlier seven-day period, November 11-17. The November 18-24 data is not much different than the earlier period. Average daily sunspot numbers are a little lower, and so are geomagnetic indices.

Currently early Monday morning a solar wind is up against Earth's magnetic field, but so far the worst effect is a K index of 3, indicating unsettled conditions, but not active. Conditions over the weekend were a little rough, with both the mid-latitude and planetary K index as high as five. The current forecast shows a moderate A index of 10 over the next few days, but active geomagnetic conditions are predicted for December 2-3. Daily solar flux values around 110 are predicted through December 1, rising a bit higher through December 5.

The nights, now longer in the Northern Hemisphere, will continue to lengthen through December 21, the winter solstice. This suggests an emphasis on the lower bands for communication, especially for those of us at higher latitudes. On December 21 Miami, Florida, will have 10 hours and 34 minutes from sunrise to sunset, but Seattle, Washington, will only have 8 hours and 40 minutes. Plotting a 10- meter daylight path from Miami to Brazil on the solstice using propagation software such as W6ELprop shows an opening four hours longer than for a path from Seattle to Brazil under the same conditions. Those in the southern states frequently have longer and better openings to the rest of the world than operators further north.

For more information concerning propagation and an explanation of the numbers used in this report, visit the ARRL Technical Information Service Propagation page.

Sunspot numbers for November 18 through 24 were 77, 61, 40, 27, 28, 45 and 72, with a mean of 50. The 10.7 cm flux was 104, 102.2, 99.3, 100.9, 106.3, 106.9 and 107.3, with a mean of 103.8. Estimated planetary A indices were 3, 4, 18, 16, 10, 5 and 6, with a mean of 8.9. Estimated mid-latitude A indices were 4, 3, 12, 9, 6, 4 and 7, with a mean of 6.4.

Amateur solar observer Tad Cook, K7RA, 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 e-mail.

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