SB PROP @ ARL $ARLP006<br />ARLP006 Propagation de K7VVV<br /><br />ZCZC AP06<br />QST de W1AW <br />Propagation Forecast Bulletin 6 ARLP006<br />>From Tad Cook, K7VVV<br />Seattle, WA February 7, 2003<br />To all radio amateurs <br /><br />SB PROP ARL ARLP006<br />ARLP006 Propagation de K7VVV<br /><br />Sunspot numbers dropped way down into the double-digits this week,<br />and compared with last week the average daily sunspot number was off<br />by nearly 51 points. Daily solar flux values declined last week and<br />then rose this week, so the average daily value for the week was<br />practically unchanged at less than two points higher. Solar flux is<br />expected to peak through next week around 170, with predicted daily<br />values for Friday through Sunday at 155, 160 and 165.<br /><br />Geomagnetic conditions were quite active this week, with the average<br />daily planetary A index up over 8 points from last week. A solar<br />wind stream caused some high A and K index values, with the peak day<br />on Sunday when the planetary A index was 45 and K indices were as<br />high as 6, indicating a geomagnetic storm. Higher latitudes were<br />even more affected, and Alaska's College A index reach 58. This made<br />higher latitude HF communications more difficult. Moderate<br />geomagnetic conditions are predicted for the next few days, but<br />Monday could be unsettled.<br /><br />January has passed, so let's look at the average daily solar flux<br />and sunspot numbers for the month to spot any trends.<br /><br />Average daily sunspot numbers for August 2002 through January 2003<br />were 191.0, 206.4, 153.9, 159.8, 144.8 and 150.0. Average daily<br />solar flux for those same months was 183.9, 175.8, 167.0, 168.7,<br />157.2 and 144.0. This shows a downward trend. For the next 45 days<br />the predicted average daily solar flux is 140.3. For the same 45<br />days last year the actual daily solar flux averaged 188.8, so going<br />into the spring, MUFs (Maximum Usable Frequencies) should be lower<br />and general HF conditions a bit poorer. But during the same period<br />in 2001 the average daily solar flux was 147.3, only seven points<br />higher than the values predicted for the next month and a half. If<br />predicted values hold up (keeping in mind that forecasting out 45<br />days is chancy) conditions going into spring at least may not be<br />worse than 2001.<br /><br />Pick a date a few weeks from now (in the middle of the 45 day period<br />mentioned above) and plug it into a popular propagation prediction<br />program. Then compare the 140.3 value for this year with 188.8 for<br />last year. This may give us some idea of how spring conditions might<br />be compared to last year. For instance, if I plot a path for March 1<br />from Texas to Brazil, 15 meters closes about four hours earlier in<br />2003 compared to 2002, and 10 meters closes about an hour and a half<br />earlier. I ran these numbers using W6ELprop, available free at<br />http://www.qsl.net/w6elprop/.<br /><br />For more information about propagation and an explanation of the<br />numbers used in this bulletin, see the Propagation page on the ARRL<br />Web site at, http://www.arrl.org/tis/info/propagation.html and,<br />especially, the article "The Sun, the Earth, the Ionosphere," by<br />Carl Luetzelschwab, K9LA.<br /><br />Sunspot numbers for January 30 through February 5 were 105, 96, 75,<br />61, 69, 77, and 89, with a mean of 81.7. 10.7 cm flux was 121.2,<br />120.4, 125.8, 126.7, 132.5, 134.8, and 140.1, with a mean of 128.8.<br />Estimated planetary A indices were 26, 18, 13, 45, 19, 24, and 12,<br />with a mean of 22.4.<br />NNNN<br />/EX