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 we reported last week! The quietest day was July 10, with a planetary A index of 8. The most active days were July 11, 12 and 16, when the planetary A index was 46, 46 and 48, respectively.
The planetary A index was 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 July 24.
On the morning of Saturday, July 12 (Friday night in North America), Earth was inside a strong solar wind coming from a coronal hole on the sun. The resulting geomagnetic storm produced auroras seen from Canada and the northern US. 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.
Bill Hohnstein, K0HA, writes from Mississippi with an exciting story about seeing a July 14 spot at 0002 UTC on a European packet cluster for his 6-meter signal. Milan, OK1FM, posted the report, which he copied even though he had no 6-meter antenna. He was using a 10-40 meter multiband Yagi. K0HA e-mailed OK1FM to confirm the spot. OK1FM reports he has a new five-element 6-meter Yagi with an 18-foot boom ready to go up. His Web site has more about his station.
Serge Stroobandt, ON4BAA, sent a link to a propagation Web site he put together. Among other features it includes a Maximum Usable Frequency (MUF) mapping program that shows the MUF calculated in all directions from any location. You might want to make sure your speakers are turned on.
Regarding recent comments about seemingly enhanced VHF propagation during geomagnetic storms, Jon Jones, N0JK, sent this quote from the book, Six Meters, A Guide to the Magic Band, by Ken Neubeck, WB2AMU: "Geomagnetic storms appear to be a detrimental factor in the formation of Sporadic-E. It is very rare for a 6-meter operator to hear a strong sporadic-E opening where there is high geomagnetic activity."
For more information on propagation and an explanation of the numbers used in this bulletin visit the Propagation page on the ARRL Web site.
Sunspot numbers for July 10 through 16 were 137, 127, 102, 137, 159, 154 and 164, with a mean of 140. The 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.