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![Previous (earlier) Story](/images/sty-down.gif "ARRL President Emeritus Jim Haynie, W5JBP, is "Amateur of the Year""){kind=small} Previous: ARRL President Emeritus Jim Haynie, W5JBP, is "Amateur of the Year" |  Next: Surfin': Becoming a Pipsqueak -- Revisited |
SEATTLE, WA, Mar 9, 2007 -- On March 1 Sunspot 944 was pointed straight at Earth. This small sunspot was followed a few days later by another small one, Sunspot 945. Sunspot 945 is visible in photos from March 5, just behind 944, but both spots seemed to disappear a day or two later before they would have rotated off the visible solar disk. Now the sun is blank, and the sunspot number is zero.
The minimum non-zero sunspot number is 11, and lately sunspot numbers move from zero to 11 to 23 or 24, and back to 11. No solar activity is expected for the next few days, so we will probably see at least several days with a sunspot number of zero.
Geomagnetic conditions are expected to remain quiet, at least until Monday or Tuesday, March 12-13. The US Air Force predicts a planetary A index for March 9-15 of 5, 5, 7, 15, 20, 15 and 10. Geophysical Institute Prague predicts quiet conditions for March 9-10, quiet to unsettled March 11, active geomagnetic conditions for March 12, unsettled to active March 13, unsettled March 14 and quiet to unsettled March 15. A recurring solar wind stream is predicted for Monday, March 12, and it should produce the expected geomagnetic instability.
New predictions for the solar minimum are showing up frequently of late. The monthly smoothed sunspot number forecast for the rest of 2007 from the NOAA Space Environment Center in the weekly Preliminary Report and Forecast has been adjusted again, the third time since the first of the year. The revised tables are on page 9 of issue 1635, and page 10 of issues 1640 and 1644.
Please note that the table in 1640 is mislabeled at the bottom of the page as 03 January. It should read 06 February.
Currently they predict a solar minimum for right now, with a smoothed sunspot number of 6 for March and April 2007, then 7, 8, 10, 11, 13, 16, 18 and 21 for the remaining eight months of this year. As mentioned in past bulletins, these are smoothed sunspot numbers, averaged over a year. So the prediction of six for this month means that if the prediction is accurate, at the end of September 2007 you could take half the average of daily sunspot numbers for that month, add it to half the average of daily sunspot numbers for September 2006, add the total to the monthly averages for each month in between, divide by 12, and get six as the result. Currently we're seeing higher values, with an average daily sunspot number of 19 for last week, 19.6 the week before, 14.6 for the week prior to that, 6.3 for the previous week, and 28.7 for the week prior to that, which was February 1-7.
The National Geophysical Data Center offers an explanation of the method for determining the 12-month smoothed sunspot number.
Jim Headrick, W3CP, of Stanfield, Oregon, sent in a different prediction from the Australian government. It has the solar minimum centered on September 2007. Note that the NOAA version mentioned previously ends in December 2007, but the one Jim sent goes through 2008 and 2009 as well. By the way, I don't know how long Jim has been a ham, but he was born early in Sunspot Cycle 15, and I'm sure he hopes to see the new Cycle 24 all the way through. See a page of all the 20th century sunspot cycles on the WM7D.net site.
We heard from another ham enjoying low-power operations at the bottom of the cycle. Bill Raiford, NI4Y, of Fredericksburg, Virginia, says he operates 10 W on 20 meters from his car. "Last week I worked VK2KM, and this week I worked VK2GWK from my 10 watt mobile station," he reports.
He continues: "No, VK isn't rare DX, but just the thought of 10 W propagating from my vehicle in VA to VK land is quite amazing. I am at 194 countries from my mobile."
Dave Green, VE5TLY, of Ottawa, Ontario, advised of an interesting BBC article concerning the new Solar Terrestrial Relations Observatory (STEREO) satellites which soon will be observing coronal mass ejections traveling through space in 3D.
For More Information
For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page and the article "The Sun, the Earth, the Ionosphere: What the Numbers Mean, and Propagation Predictions," by Carl Luetzelschwab, K9LA. An archive of past bulletins is on the ARRL Web site. The propagation charts that formerly appeared in QST now are available on the QST Propagation Charts page on the ARRL Web site.
Weekly Sunspot Numbers
Sunspot numbers for March 1 through 7 were 11, 23, 11, 24, 27, 26 and 11, with a mean of 19. 10.7 cm flux was 74.8, 75.5, 73.3, 72.5, 71.9, 71.9, and 72.9, with a mean of 73.3. Estimated planetary A indices were 11, 5, 2, 3, 8, 18 and 14, with a mean of 8.7. Estimated mid-latitude A indices were 7, 4, 0, 4, 6, 14 and 12, with a mean of 6.7.
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 appears in The ARRL Letter. Readers may contact the author via e-mail.
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