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Science/Tech See other Science/Tech Articles Title: K7RA Solar Update The K7RA Solar Update Our Sun is still very quiet, but last week's Propagation Forecast Bulletin ARLP035 mentioned a new sunspot emerging on August 21-22. Spaceweather.com showed the sunspot number on those days as 11, which is the smallest non-zero sunspot number. Because of the way the daily sunspot number is calculated, one sunspot gets ten points for one group, and one point for one sunspot within that group. Five sunspots in three groups yields a daily sunspot number of 35. But the official sunspot number from NOAA showed zero on both days. You can see it for yourself at, http://www.swpc.noaa.gov/ftpdir/indices/DSD.txt. It seems that this little spot that tried to emerge never grew large enough to be counted as a sunspot. Instead it was just a little magnetic wrinkle, but one interesting aspect was the polarity indicated a Cycle 24 event, not Cycle 23 as we reported last week. John Andrews, W1TAG of Holden, Massachusetts wrote, "Your current report on the ARRL website indicates that the tiny sunspot presently visible is from the old solar cycle. The current Mt. Wilson magnetogram data shows a dipole with the south pole leading the north, which in the northern hemisphere indicates a new cycle spot." In a subsequent message, John wrote, "On the other hand, those of us playing at 505 and 137 kHz are quite delighted with the quiet Sun! A little kick every now and then to recharge the supply of free electrons, and we're all set. The transatlantic stuff is MUCH easier than it was 4-5 years ago. Oh well, the pendulum will swing the other way with a vengeance, I'm sure. Then you'll be happy, and I'll be sad." If we don't see any sunspots this weekend, Sunday will mark 42 consecutive days with no sunspots. This will also bring the 3-month moving average for daily sunspot numbers (that we present monthly) clear down to 1.76, the lowest on this side of Cycle 23. This would be the three month average centered on July. That makes the 3-month moving average for the past 14 months look like this: We calculated the July 2008 average by adding together all daily sunspot numbers from June 1 through August 31, then dividing by 92, the number of days in that period. Likewise, the June 2008 average used the sum of all sunspot numbers from May 1 through July 31. You can see why many thought the minimum was last October, but we've instead reached a new low for the recent period. The forecast for the next week is a planetary A index of 5 on every day, indicating more of the same quiet and stable geomagnetic conditions. The prediction for September 5 is a planetary A index of 18, probably from a recurring coronal hole and associated solar wind. Geophysical Institute Prague predicts quiet conditions August 29 to September 3, and quiet to unsettled September 4. Jim Henderson, KF7E of Queen Creek, Arizona notes that over the past few days (August 25-27) at 1400z-1600z during his local morning hours, conditions on 20 meters to Europe, across UA3/4/9/0 and Asia have been great. With no sunspots, he sees good effects from solar wind streams energizing these paths. But on Thursday, August 28 he noted an upswing in solar wind at, http://www.swpc.noaa.gov/ace/MAG_SWEPAM_6h.html and reinforced the observation with data at, http://www.swpc.noaa.gov/rt_plots/bou_12h.html. This caused a decline in conditions, but at 1445z he noted copyable signals from EY8/K4ZW in Tajikistan on 14.2176 MHz. He noted that HS0ZEE (Chiang Mai, Thailand) seemed to be coming strongest from the northeast, 90 degrees away from normal headings and with pronounced echo and rapid auroral flutter. Randy Crews, W7TJ of Spokane, Washington, offered this on August 27 in a message titled "Bumping along the bottom": "I see we have been spotless now for 37 straight days, which I think exceeds the number of spotless days in October of 2007 and could possibly exceed the 6 week period of spotless days we had in Sept/Oct of 1996. Possibly this month could set a double minimum in Cycle 23. One thing that has really helped the Bands in the last few days along with A and K indices of 0-2 is that the Sun is void of any Coronal disturbances....BIG difference! If we could get some Cycle 24 spots, we would surely be off and running! As it has been said, it's darkest just B4 dawn." If you would like to make a comment or have a tip for our readers, email the author at, k7ra@arrl.net. For more information concerning radio propagation, see the ARRL Technical Information Service web page at, http://www.arrl.org/tis/info/propagation.html. For a detailed explanation of the numbers used in this bulletin see, http://www.arrl.org/tis/info/k9la-prop.html. An archive of past propagation bulletins is at, http://www.arrl.org/w1aw/prop/. Monthly propagation charts between four USA regions and twelve overseas locations are at, http://www.arrl.org/qst/propcharts/. Instructions for starting or ending email distribution of this bulletin are at http://www.arrl.org/w1aw.html#email. Sunspot numbers for August 21 through 27 were 0, 0, 0, 0, 0, 0, and 0 with a mean of 0. 10.7 cm flux was 67.1, 67.6, 67.9, 67.1, 66.6, 66.9, and 66.6 with a mean of 67.1. Estimated planetary A indices were 4, 4, 2, 4, 2, 3 and 3 with a mean of 3.1. Estimated mid-latitude A indices were 4, 2, 2, 2, 1, 1 and 2 with a mean of 2.
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