ARRL

ARRL Propagation Bulletin ARLP007 (2001)

SB PROP @ ARL $ARLP007
ARLP007 Propagation de K7VVV

ZCZC AP07
QST de W1AW  
Propagation Forecast Bulletin 7  ARLP007
From Tad Cook, K7VVV
Seattle, WA  February 16, 2001
To all radio amateurs 

SB PROP ARL ARLP007
ARLP007 Propagation de K7VVV

The quiet sun period continues, as the sunspot number dropped below
100 and solar flux went down to 137.9 on Wednesday. The last two
times that solar flux values were this low were on December 9 and
September 13 of last year. Average solar flux for the past week was
down almost 15 points and average sunspot numbers were off by over 5
points, when compared to the previous week. The forecast for the
next few days has solar flux dropping to 135 on Friday and Saturday,
and bottoming out around 130 on Sunday and Monday. It is then
expected to rise rapidly from 135 to 165 between February 21- 23.

Despite the relatively quiet sun, there was some geomagnetic
activity this week. The earth entered a high speed solar wind stream
on Tuesday, and the results were planetary A indices of 19 and 17 on
Tuesday and Wednesday, with planetary K indices as high as 4 over
much of the two days. The high latitude College A index was 24 and
26, and over a few periods the College K index was 5. This wind
stream was probably the result of a coronal mass ejection that
occurred on Sunday. Fortunately, the bulk of this ejected mass
missed us, but there was enough to trigger some unsettled conditions
as well as higher absorption of HF radio signals over polar paths.

Conditions should be relatively settled for the ARRL International
DX CW Contest this weekend, and with the days getting a little
longer, we should see a little more spring-like propagation on HF.

KA7TON wrote recently asking about the sun's magnetic poles
reversing during the peak of every solar cycle. At the time I could
not recall the details, but now there have been some news items on
this subject over the past week. A story on a NASA web site at
http://science.msfc.nasa.gov/headlines/y2001/ast15feb_1.htm says
that the switch has already happened, and that this is a good
indication that the peak of the solar cycle is here, or perhaps has
passed. Apparently the earth's magnetic field also does this, but
reversals are between five thousand and fifty-million years apart
instead of every eleven. More info on solar magnetic fields can be
found at http://science.nasa.gov/ssl/pad/solar/dynamo.htm .

Readers may also want to check the March 2001 issue of Worldradio
magazine for the propagation column by K9LA. Carl writes about the
10.7 cm solar flux value, and how it may not be the best indicator
for daily propagation conditions.

Now we will present a few path predictions for the DX contest this
weekend. We will use a solar flux value of 145.5, which is average
for the last seven days and the next three. These are good bets for
when the bands should be open between average amateur stations. The
West Coast location is centered on San Francisco, and the East Coast
center is on Washington, D.C. Conditions will vary as you move away
from these areas. For instance, in the West Coast 10 meter path
projection to Europe, the prediction is for a possible opening
around 1730z. Move north to Seattle, and this opening seems to
disappear, but move south to Los Angeles, and it looks like a fairly
good bet from 1700-1830z. The ones marked best are stable periods of
what should be strong signals. Good luck in the contest.

From the East Coast of the U.S., to Western Europe, 80 meters 2200-
0830z (best 0100-0630z), 40 meters 2030-1000z (best 2300-0700z), 20
meters 1300-0030z (best 2230-2330z), 15 meters 1330-2000z, 10 meters
1600-1730z. To Southern Africa, 80 meters 2230-0430z, 40 meters
2200-0500z, 20 meters 1930-0330z and 0600-0630z, 15 meters
1600-2300z, 10 meters 1330-2000z. To South America, 80 meters
2330-1000z, 40 meters 2230-1000z, 20 meters 2030-0730z and
1100-1200z, 15 meters 1300-2330z, 10 meters 1400-2100z. To
Australia, 80 meters 0930-1230z, 40 meters 0900-1300z, 20 meters
1300-1500z, 15 meters 1430-1530z, 10 meters possibly around
2200-2300z. To Japan, 80 meters 0830-1230z, 40 meters 0730-1300z, 20
meters 1330- 1700z and 2030-2330z, 15 meters possibly around 2200z,
10 meters possibly around 2230z.

From the center of the continental U.S. to Western Europe, 80 meters
2300-0900z (best 0230-0630z), 40 meters 2130-1100z (best
0030-0700z), 20 meters 1330-0100 (gradually stronger toward the end
of the period), 15 meters 1430-2030z, 10 meters 1630-1800z. To
Southern Africa, 80 meters 0000-0430z (best 0230-0430z), 40 meters
2330-0500z, 20 meters 2100-0300z, 15 meters 1700-2330z (stronger
signals later in the period), 10 meters 1530-2100z. To South
America, 80 meters 0000-1000z, 40 meters 2330-1030z, 20 meters
2200-1130z, 15 meters 1330-0130z, 10 meters 1430-2300z. To
Australia, 80 meters 1030-1400z, 40 meters 0900-1430z, 20 meters
0730-1630z, 15 meters and 10 meters possibly around 1530z. To Japan,
80 meters 0800-1430z, 40 meters 0700-1430z (best 0900-1300z), 20
meters 1430-1800z, 15 meters 2130-0200z, 10 meters 2230-2300z.

From the West Coast of the U.S. to Western Europe, 80 meters 0130-
0830z, 40 meters 0030-1000z (best 0230-0630z), 20 meters 1430-2100z
and 2200-2330z, 15 meters 1600-1930z, 10 meters possibly around
1730z. To Southern Africa, 80 meters 0130-0430z, 40 meters
0030-0500z, 20 meters 2200-0500z, 15 meters 1900-0000z, 10 meters
1830-2130z. To South America, 80 meters 0200-1000z (best
0430-0900z), 40 meters 0100-1100z (best 0230-0930z), 20 meters
2300-1100z (best 0200-0930z), 15 meters 1430-0300z, 10 meters
1530-0130z. To Australia, 80 meters 1030-1500z, 40 meters
0900-1600z, 20 meters 0730-1730z, 15 meters 2000-2100z and
0400-0500z, 10 meters 2330-0230z. To Japan, 80 meters 0730-1530z, 40
meters 0700-1630z, 20 meters 0330-0830z and 1530-1830z, 15 meters
2130-0400z, 10 meters 2230-0130z.

Sunspot numbers for February 8 through 14 were 168, 179, 172, 169,
106, 113 and 99 with a mean of 143.7. 10.7 cm flux was 156.5, 162.4,
160.7, 151.3, 144.6, 141.3 and 137.9, with a mean of 150.7, and
estimated planetary A indices were 6, 4, 5, 7, 4, 19 and 17 with a
mean of 8.9.
NNNN
/EX