ZCZC AP17
QST de W1AW
Propagation Forecast Bulletin 17 ARLP017
From Tad Cook, K7VVV
Seattle, WA April 26, 2002
To all radio amateurs
SB PROP ARL ARLP017
ARLP017 Propagation de K7VVV
Big news this week were the geomagnetic storms. Stormy conditions reigned continuously from Wednesday through Saturday and the geomagnetic indices rose again on Tuesday.
K9IIK wrote to say he thought something was wrong with his radio, which is a common reaction when conditions are truly awful and HF radio signals are either weak or never heard at all. A check of geomagnetic data with a web browser pointing toward gopher://solar.sec.noaa.gov/00/latest/DGD tells the story. Most HF operators are comfortable when the A index is 10 or lower and the K index is 3 or below.
K9IIK asked if this was a sign of things to come. It is true that conditions are less stable after a peak in sunspot activity than before, but conditions are bound to settle down. Currently it looks like geomagnetic indices could rise again on Saturday, but to a level indicating unsettled conditions rather than a storm.
Looking at the numbers, both sunspots and solar flux were lower this week, with average sunspot numbers down nearly 38 points and average daily solar flux off by over 28 points. Sunspot count and solar flux reached a minimum on Monday and are on the way back up. Solar flux is expected to return to 200 around May 1, and may peak around 215 May 4-5.
NN4X reports from Central Florida that Saturday morning had good 6-meter conditions. Around 1500z he worked Europe on 6, and South America was coming in around the same time. Stations local to him reported loud and delayed echoes from each other's signals, to the point that they could barely copy each other. About five hours later there was an opening toward the Pacific.
W5XC near Houston reports that he worked FO3BM on April 18 at 1015z on 6-meters. He recommends checking out the http://6m.dxers.info/ site during these openings.
WV1K writes from Massachusetts that real time data on D-region absorption is at http://www.sel.noaa.gov/rt_plots/dregion.html. D-region absorption is a major cause of attenuation of HF radio signals, and a good treatise on this is can be found at http://www.sel.noaa.gov/rt_plots/dregionDoc.html.
Sunspot numbers for April 18 through 24 were 160, 182, 185, 160, 155, 180 and 256 with a mean of 182.6. 10.7 cm flux was 188.2, 179.7, 177.3, 173.4, 169.9, 175.3 and 176.9, with a mean of 177.2, and estimated planetary A indices were 54, 44, 62, 7, 12, 22 and 7 with a mean of 29.7.