ARLP011 Propagation de K7RA:
March 14, 2003

Propagation Forecast Bulletin 11 ARLP011
From Tad Cook, K7RA
Seattle, WA March 14, 2003
To all radio amateurs

ARLP011 Propagation de K7RA

Average daily solar flux and sunspot numbers were up again this week. Average daily sunspot numbers, which were up nearly 50 points last week compared to the previous week, this week rose nearly 70 points compared to last week. Average daily solar flux was up 30 points last week and over 7 points this week. Solar flux is expected to decline to just above 100 from March 20-24, around the time of the solar equinox.

There is a large coronal hole responsible for a solar wind stream heading our way. It could result in some active geomagnetic conditions this weekend, but so far only unsettled conditions are predicted through Sunday, with a planetary A index around 15.

Note that the vernal equinox is coming up this week, a wonderful time for HF propagation. On the first day of spring the night and day will be exactly 12 hours each, all over the world, from the equator to the poles. Over the winter in the northern hemisphere, signals traveling to the southern hemisphere have to deal with summertime propagation modes.

At either equinox (autumnal or vernal) the whole earth is blessed with an even distribution of solar radiation.

For more information about propagation and an explanation of the numbers used in this bulletin, see the Propagation page on the ARRL Web site at, and especially the article "The Sun, the Earth, the Ionosphere," by Carl Luetzelschwab, K9LA.

Sunspot numbers for March 6 through 12 were 132, 191, 203, 224, 214, 142, and 109, with a mean of 173.6. 10.7 cm flux was 150.3, 149.9, 148.3, 152.7, 143.7, 141.5, and 138, with a mean of 146.3. Estimated planetary A indices were 25, 14, 9, 11, 16, 13, and 9, with a mean of 13.9.