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The K7RA Solar Update


The average daily sunspot numbers over the past reporting week (March 8-14) were 88.3, a rise of nearly 19 points; the average daily solar flux rose more than 12 points to 134.2. Sunspot numbers for March 8-14 were 86, 96, 89, 103, 89, 80 and 75, with a mean of 88.3. The 10.7 cm flux was 139.5, 145.5, 148.9, 131.2, 114.9, 140.7 and 118.8, with a mean of 134.2. The estimated planetary A indices were 24, 68, 18, 8, 28, 10 and 8, with a mean of 23.4. The estimated mid-latitude A indices were 21, 57, 17, 10, 28, 10, and 6, with a mean of 21.3

Four new sunspots have emerged. The first was sunspot group 1432 on March 9, which began with a relative area of 90. In the days following, it went to 80, 50, 80, 70, 60 and 100. Two more sunspot groups -- numbered 1433 and 1434 -- appeared on March 11, with a combined relative area (in millionths of a solar hemisphere) of 240, then 130, 140, 150 and 150. Finally, on March 15, new sunspot group 1435 emerged, with a relative size of 30. The daily sunspot number on this day rose to 85.

The sunspot number peaked on March 11 at 103, and the solar flux on March 10 at 148.9 and again on March 13 at 140.7. The outlook for the next few days has solar flux at 110 on March 16, 105 on March 17-21, 110 on March 22-23, back down to 105 on March 24-27 and then 110, 115 and 125 on March 28-30, and rising to 130 on March 31-April 5.

There was a great deal of geomagnetic activity on March 9, with a planetary A index at 68, and again on March 12 with planetary A index of 28. An M-class x-ray flare occurred on March 15 at 0752 UTC, and if you catch it soon enough, you can see the resulting x-ray flux on the GOES monitor.

The predicted planetary A index for March 16-17 are 18 and 10, then 5 for March 18-27, 10 on March 28, 8 on March 29-31, 5 on April 1-2, 8 on April 3-4 and 5 on April 5-9. The vernal equinox will occur at 0514 UTC on March 20. The shift to spring generally means favorable conditions for HF propagation

Thanks to Howard Lester, N7SO, who sent in a photo of a backyard telescope in Brooklyn, New York owned by Alan Friedman and operated among city lights. Howard also sent this solar image from March 11 using the same telescope, with appropriate filters, of course, and a detail of region 1429. NASA also posted a nice image plus a video of sunspot region 1429.

Scott Woelm, WX0V, of Fridley, Minnesota wrote: “Bob Conzemius, KB0ZXT, of Grand Rapids, Minnesota has some rather spectacular time-lapse video of aurora displays

All times listed are UTC, unless otherwise noted.

Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. You can find a guide to articles and programs concerning propagation here. Check here and here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.



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