SB PROP @ ARL $ARLP039<br />ARLP039 Propagation de K7RA<br /><br />ZCZC AP39<br />QST de W1AW <br />Propagation Forecast Bulletin 39 ARLP039<br />>From Tad Cook, K7RA<br />Seattle, WA September 16, 2005<br />To all radio amateurs <br /><br />SB PROP ARL ARLP039<br />ARLP039 Propagation de K7RA<br /><br />This week the Sun has given us a tremendous amount of activity in<br />the form of large solar flares. A geomagnetic storm is still in<br />progress, and the planetary A index from Saturday through Thursday,<br />September 10-15, was 30, 105, 66, 51, 25 and 43. These are high<br />numbers.<br /><br />The average planetary A index for this week more than doubled to<br />43.1. Average daily sunspot numbers more than quadrupled to 71.1.<br />These numbers compare the 7 days ending Wednesday, September 14 with<br />the previous 7 day period.<br /><br />Next week is the Northern Hemisphere's Autumnal Equinox. This period<br />could be a good one for HF propagation if solar flares quiet down<br />and the sunspot count doesn't sink back toward 0. The sunspot number<br />rose above 100 on Sunday, September 11, the first time since August<br />3.<br /><br />The source of all this excitement is a single large sunspot group,<br />number 798. This spot was just peeking around the edge of the<br />visible solar disk on September 9, but by September 14-15 it was<br />aimed squarely at our planet. The last time around it was much<br />smaller and still emerging, visible until August 24. Although not<br />aimed at Earth on September 7, that day it produced an X17 solar<br />flare, the fourth largest detected over the past three decades.<br />Over the next week it produced 8 more flares, each causing HF radio<br />blackouts.<br /><br />Of course, VHF operators probably didn't mind all the disruption.<br />You can check the 50 MHz Propagation Logger page at,<br />
http://dxworld.com/50prop.html to see what they've been up to on<br />6-meters, and,
http://dxworld.com/files/vhfprop22.htm for a further<br />look back.<br /><br />Steve Lyon, WB6RIB and several others sent in an article from NASA<br />about all this activity in the year before the solar cycle bottom,<br />titled "Solar Minimum Explodes." You can read it for yourself on the<br />
http://science.nasa.gov/headlines/y2005/15sep_solarminexplodes.htm<br />web site.<br /><br />Over the next few days look for declining geomagnetic numbers, but<br />fairly good sunspot and solar flux values. (Remember, HF operators<br />generally want the sunspot and the somewhat-related solar flux<br />numbers to remain high, with the geomagnetic A index and related K<br />index as low as possible). Predicted solar flux for Friday through<br />Monday, September 16-19 is 115, 110, 110 and 105. The predicted<br />planetary A index for those same days is 25, 15, 10 and 10.<br />Geophysical Institute Prague predicts active to minor storm<br />conditions for September 16, active conditions on September 17 and<br />20, unsettled to active conditions September 21, unsettled<br />conditions for September 18 and 22, and quiet to unsettled<br />conditions on September 19.<br /><br />Ed Douglass, AA9OZ is trying for his second 5-Band DXCC award. The<br />first time around was as 7P8DX in Lesotho from 1986-1992, and this<br />time he wants to do it from Sturgeon Bay, Wisconsin, a town just<br />below the 45th parallel on a peninsula extending into Lake Michigan.<br />He aims to work 100 countries on 75 and 80 meters during the sunspot<br />minimum, and asked if the absence of sunspots might improve his<br />chances on lower frequencies. Certainly the MUF (Maximum Usable<br />Frequency) is lower with fewer sunspots, so openings on 20-15-10<br />meters are much less common. But I seemed to recall Carl<br />Luetzelschwab, K9LA having something to say about the absence of<br />solar activity producing better conditions overall on the low<br />frequencies.<br /><br />Carl referred me to an interesting article he wrote for the<br />September/October 2005 issue of "The DX Magazine" titled "Getting<br />Ready for Solar Minimum." Among other issues, the article discusses<br />what happens with 160 and 80 meter propagation passing through the<br />auroral zone. This includes West Coast North America to Europe,<br />Midwest to Europe and Japan, and East Coast to Japan paths. During<br />the solar minimum, there is less chance of ionospheric disturbance<br />in northern latitudes. Carl writes, "In general, a quiet high<br />latitude ionosphere provides the best propagation on the lower bands<br />for paths near or going through the auroral zone."<br /><br />Although this excellent article is not online, you can find similar<br />material by entering a query for +K9LA +"auroral zone" in a search<br />engine such as Google. One link returned was for another of our<br />bulletins, ARLP008 from 2004, which talked about this same issue,<br />and mentions that Carl wrote about this in the March 2004 issue of<br />WorldRadio. The bulletin is located at,<br />
http://www.arrl.org/w1aw/prop/2004-arlp008.html. You can find out<br />more about "The DX Magazine" at
http://www.dxpub.com/. You can also<br />look at current conditions in the auroral zone north of North<br />America at,<br />
http://www.spaceweather.gc.ca/forecastmap_e.shtml.<br /><br />Terry Oldham, KH6MT wrote asking about 10 meters, an often difficult<br />band at the bottom of the cycle. He lives in North Central Florida,<br />between Jacksonville and Tampa, and wants to know when 10 might be<br />open to El Paso, Texas next. He mentioned that the window used to<br />run from September through April, but last year he saw no window at<br />all.<br /><br />I told Terry about W6ELprop (the free propagation program for the<br />PC, from
http://www.qsl.net/w6elprop/) and mentioned he could plug<br />in numbers for that path to see what pops up. I tried it, and over<br />the approximately 1500 miles at this time of year, a sustained<br />sunspot number a little higher than we've seen recently would help.<br />Still, if you plug in the average sunspot number for the past week<br />(71.1), according to this program propagation is quite possible.<br />With about 10 more points, or perhaps going over to the 12 meter<br />band, the odds look quite good.<br /><br />If you would like to comment or have a tip, email the author at,<br />k7ra@arrl.net.<br /><br />For more information concerning radio propagation and an explanation<br />of the numbers used in this bulletin see the ARRL Technical<br />Information Service propagation page at,<br />
http://www.arrl.org/tis/info/propagation.html. An archive of past<br />bulletins is found at,
http://www.arrl.org/w1aw/prop/.<br /><br />Sunspot numbers for September 8 through 14 were 36, 59, 59, 101, 62,<br />95 and 86 with a mean of 71.1. 10.7 cm flux was 94.1, 99, 116,<br />109.7, 118, 114, and 116.6, with a mean of 109.6. Estimated<br />planetary A indices were 8, 17, 30, 105, 66, 51 and 25 with a mean<br />of 43.1. Estimated mid-latitude A indices were 5, 12, 15, 53, 32, 26<br />and 13, with a mean of 22.3.<br />NNNN<br />/EX
