Select as required  Propagation MAXIMUM USABLE FREQUENCIES (MUFs) To see the current MUF image of the world please click on this line   THE SUNSPOT NUMBER Scientists track solar cycles by counting sunspots -- cool planet-sized areas on the Sun where intense magnetic loops poke through the star's visible surface. Counting sunspots is not as straightforward as it sounds. Suppose you looked at the Sun through a pair of (properly filtered) low power binoculars -- you might be able to see two or three large spots. An observer peering through a high-powered telescope might see 10 or 20. A powerful space- based observatory could see even more -- say, 50 to 100. Which is the correct sunspot number? There are two official sunspot numbers in common use. The first, the daily "Boulder Sunspot Number," is computed by the NOAA Space Environment Center using a formula devised by Rudolph Wolf in 1848: R=k (10g+s) where R is the sunspot number; g is the number of sunspot groups on the solar disk; s is the total number of individual spots in all the groups; and k is a variable scaling factor (usually <1) that accounts for observing conditions and the type of telescope (binoculars, space telescopes, etc.). Scientists combine data from lots of observatories -- each with its own k factor -- to arrive at a daily value. Above: International sunspot numbers from 1745 to the present. The Boulder number (reported daily on SpaceWeather.com) is usually about 25% higher than the second official index, the "International Sunspot Number," published daily by the Solar Influences Data Center in Belgium. Both the Boulder and the International numbers are calculated from the same basic formula, but they incorporate data from different observatories. As a rule of thumb, if you divide either of the official sunspot numbers by 15, you'll get the approximate number of individual sunspots visible on the solar disk if you look at the Sun by projecting its image on a paper plate with a small telescope. LATEST PROPAGATION NEWS FROM THE ARRL Made with Xara Web Designer 6 Propagation Forecast Bulletin 34  ARLP034 From Tad Cook, K7RA Seattle, WA  August 27, 2010 To all radio amateurs SB PROP ARL ARLP034 ARLP034 Propagation de K7RA As I was writing the bulletin overnight my desktop PC was hit by a drive-by virus that downloaded itself automatically when viewing sunspot images on an infected website.  Unable to remove the malware by morning, the bulletin was rewritten on another PC, and some of the topics that were planned had to be skipped for now.  The image was of a large sunspot in sunspot group 1084, from the New Solar Telescope at Big Bear Solar Observatory in California.  The infected site was one of many news sites carrying the image. Spaceweather.com provides a nice uninfected image file at http://snipurl.com/10trag. This week saw three days (August 21-23) with no sunspots, and the average daily sunspot numbers for the week (August 19-25) declined over 28 points to 8, compared to the previous week.  Average daily solar flux was down more than 8 points to 75.3.  The last period of three days or more with zero sunspots ended on May 20, 2010, around 100 days ago. Sunspot group 1100 disappeared on August 21 and returned August 25. In this case, the sunspot group didn't transit the non Earth facing side of the sun, but it just faded from view, returning just as it is about to rotate off of the sun's western limb.  Sunspot group 1101 appeared on August 24, and on August 25 had grown to three times its initial size.  Daily sunspot numbers for August 24-26 were 11, 23 and 23. Remember that the sunspot number is not the same as the number of sunspots. The smallest non- zero sunspot number is 11, and gets 10 points for being a sunspot group, and one point for containing one sunspot.  The sunspot number of 23 on August 25-26 represents two sunspot groups, at ten points each, one containing one sunspot (1 point) and the other containing two sunspots (2 points).  On August 25 it appears that a new smaller sunspot may be emerging between the eastern horizon and sunspot group 1101. A stiff solar wind from a coronal hole increased geomagnetic activity, and the planetary A index for August 21-26 was 3, 4, 7, 18, 20 and 11.  The latest projection shows this decreasing, with the planetary A index on August 27-28 at 10 and 8, followed by a quiet reading of 5 until September 19.  Solar flux for the same period is expected to be 75 for August 27 to September 3, then 85 on September 4-5.  Several weeks from now is the fall equinox, which is a good time for HF propagation.  The autumnal equinox will be at 0309 UTC on September 23, 2010. David Moore of Morro Bay, California sent in another article about the weak sun and solar conveyor belt, this time from the National Science Foundation.  Read it at http://snipurl.com/10trml. Jeff Hartley, N8II of Shepherdstown, West Virginia sent this on August 23: "Lots of great over and near-the-pole propagation was a daily occurrence on 17 and 20 meters since Thursday the 19th here.  The RDA Russian contest was a blast with many new Russian vanity calls in many areas of Asia worked here.  It's interesting to note that around 0100 local (2100Z) in European Russia there was a nice opening from UA1 to UA6 into here on 20 meters, whereas only UA6 was workable in the 2-3 hours before that.  I love the calls like RG8U, RG6G, R7AA, R9DX, etc.  Around 0140Z I actually had a very nice run of Russian Asians from Zone 17-18 at around 80-100 per hour for about 25-30 minutes.  UA0YAY in Zone 23 was loud on CW.  Signals from the big guns were S9+.  17 meters has been open daily to SE Asia around 1300-1430Z.  Over the past few days I have heard YB4IR, and worked VR2XMT, 9M6NRO, 9V1DE, UA0SV and some JAs, most with good signals.  15 was pretty punk until today when a few Europeans were finally heard around 1500Z".   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 at http://arrl.org/propagation-of-rf-signals.  For an explanation of the numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere.  An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation.  Find more good information and tutorials on propagation at http://mysite.ncnetwork.net/k9la/index.html. Monthly propagation charts between four USA regions and twelve overseas locations are at http://arrl.org/propagation. Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins. Sunspot numbers for August 19 through 25 were 11, 11, 0, 0, 0, 11, and 23 with a mean of 8.  10.7 cm flux was 77.9, 77.1, 75.5, 74.6, 74.9, 73.6 and 73.5 with a mean of 75.3.  Estimated planetary A indices were 5, 4, 3, 4, 7, 18 and 20 with a mean of 8.7.  Estimated mid-latitude A indices were 3, 1, 3, 0, 5, 13 and 15 with a mean of 5.7. NNNN /EX RETURN TO TOP Please note All data on this website has been taken from various sources including the ARRL, IARU and the RSGB with permission.  The data is provided as a source of information to radio amateurs and no guarantee to accuracy can be given.  Accordingly, you are recommended to check out all data with the original providers for confirmation of its validity in case of any queries that may arise. Made with Xara Web Designer 6