ARRL

ARRL Propagation Bulletin ARLP017 (2002)

SB PROP @ ARL $ARLP017
ARLP017 Propagation de K7VVV

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.
NNNN
/EX