ZCZC AP29
QST de W1AW
Propagation Forecast Bulletin 29 ARLP029
From Tad Cook, K7RA
Seattle, WA July 18, 2003
To all radio amateurs
SB PROP ARL ARLP029
ARLP029 Propagation de K7RA
Stormy space weather returned this week. The average daily planetary
A index is over twice the value reported in last week's bulletin.
The quietest day was July 10, with a planetary A index of 8, and the
most active days were July 11, 12 and 16, when the planetary A index
was 46, 46 and 48.
The planetary A index is expected to quiet down for Friday, July 18,
then rise to 15, 20 and 25 for July 19-21. Solar flux is expected to
remain around 135 to 145 through the rest of July, with a somewhat
higher value possible on July 24.
On the morning of Saturday, July 12, earth was inside a strong solar
wind coming from a coronal hole on the sun. This was actually Friday
night in North America, and the resulting geomagnetic storm produced
auroras seen from Canada and the northern United States. Then on
July 16 another solar wind, weaker than the earlier one caused a
moderate geomagnetic storm, although the planetary A index was
marginally higher. The mid-latitude A index though was much lower on
July 16 compared to July 11.
For more information on propagation and an explanation of the
numbers used in this bulletin see the Propagation page on the ARRL
Web site at
http://www.arrl.org/tis/info/propagation.html. Sunspot numbers for July 10 through 16 were 137, 127, 102, 137, 159,
154, and 164, with a mean of 140. 10.7 cm flux was 122.8, 122,
121.5, 126.5, 127.2, 125.8, and 133.1, with a mean of 125.6.
Estimated planetary A indices were 8, 46, 46, 14, 15, 27, and 48,
with a mean of 29.1.
NNNN
/EX