SB PROP @ ARL $ARLP029<br />ARLP029 Propagation de K7VVV<br /><br />ZCZC AP29<br />QST de W1AW <br />Propagation Forecast Bulletin 29 ARLP029<br />>From Tad Cook, K7VVV<br />Seattle, WA July 12, 2002<br />To all radio amateurs <br /><br />SB PROP ARL ARLP029<br />ARLP029 Propagation de K7VVV<br /><br />Conditions are still a bit in the doldrums, with solar flux and<br />sunspot numbers fairly flat. This week average daily sunspot numbers<br />were up over 24 points and average daily solar flux was down nearly<br />12 points, when compared to the previous week. Of course this seems<br />low compared to the great conditions last fall, but the numbers are<br />slightly higher than they were for the same week last year.<br /><br />In the July 13 Propagation Forecast Bulletin last year covering July<br />5-11, 2001, average sunspot numbers were only 98.1 and average solar<br />flux was 124.6. One thing that skewed the numbers a bit this time<br />was on the last day of last week's reporting period the solar flux<br />jumped unusually high, and the next day, which was the first day of<br />the current reporting period (July 5), it was now the sunspot number<br />that was high.<br /><br />The current outlook is for a slowly rising solar flux of 135 for<br />July 12-13, 140 for July 14-15, and 145 for July 16-17. There isn't<br />any forecast for higher numbers above this narrow range for the near<br />future. The prediction for the planetary A index for Friday through<br />Monday is 8, 15, 10 and 8. There is a new large sunspot coming<br />around the sun's northeast limb, and another large spot on the sun's<br />far side, as detected by helioseismic holography imaging. It has<br />been a while since this imaging scheme was mentioned in this<br />bulletin, and you can read more about it at<br />
http://spaceweather.com/glossary/farside.html.<br /><br />A good source for an explanation of shortwave propagation and some<br />of the numbers used in this bulletin (by K9LA) is at<br />
http://www.arrl.org/tis/info/k9la-prop.html. This is part of the<br />ARRL Technical Service propagation page at<br />
http://www.arrl.org/tis/info/propagation.html.<br /><br />This week our earth has reached its aphelion, the farthest distance<br />from the sun in its annual orbit. Earth's orbit has an eccentricity<br />of 1.7 percent, and this week we are nearly 95 million miles from<br />our closest star. When we are at the closest point, or perihelion,<br />we are almost 92 million miles from the sun. There was an article on<br />
http://www.cnn.com saying that the aphelion will be this Saturday,<br />but according to the U.S. Naval Observatory at<br />
http://aa.usno.navy.mil/data/docs/EarthSeasons.html it was on July<br />6. The perihelion for 2002 was January 2, and in 2003 and 2004 it<br />will be January 4.<br /><br />In this bulletin we report the observed solar flux from the Dominion<br />Radio Astrophysical Observatory in Penticton, British Columbia,<br />about 160 miles east of Vancouver. They have a nice web site at<br />
http://www.drao.nrc.ca.<br /><br />Energy is measured at 2.8 GHz with a parabolic dish pointed at the<br />sky. Of course this value would vary somewhat with the distance from<br />the observation point to the sun. So to account for this difference<br />and give a measurement that might be more indicative of the level of<br />energy from the sun at that frequency, there is an adjusted value of<br />solar flux. On July 6 at the aphelion the observed solar flux at<br />2000z was 133.5, but the adjusted flux value was 138. At the<br />perihelion the observed 2000z flux was 231.1, but the adjusted value<br />was adjusted down to 223.5. April 2 or 3 must be about half way in<br />between, and the observed and adjusted values on those days are<br />quite close. You can see a very large table of the solar flux values<br />measured thrice daily at<br />
http://www.drao.nrc.ca/icarus/www/current.txt.<br /><br />Sunspot numbers for July 4 through 10 were 175, 149, 123, 121, 125,<br />129 and 118, with a mean of 134.3. 10.7 cm flux was 146.3, 138.8,<br />133.5, 136.9, 130.9, 136.3, and 128.8, with a mean of 135.9.<br />Estimated planetary A indices were 7, 13, 23, 11, 10, 16, and 11,<br />with a mean of 13.<br />NNNN<br />/EX
