ARRL

ARRL Propagation Bulletin ARLP004 (2000)

SB PROP @ ARL $ARLP004
ARLP004 Propagation de K7VVV

ZCZC AP04
QST de W1AW  
Propagation Forecast Bulletin 4  ARLP004
From Tad Cook, K7VVV
Seattle, WA  January 28, 2000
To all radio amateurs 

SB PROP ARL ARLP004
ARLP004 Propagation de K7VVV

The predicted geomagnetic storm for last weekend turned up a day
late and with some lower numbers. Instead of peaking with a
planetary A index of 35 on Saturday, the big number was 25 on
Sunday. Conditions settled back toward normal on Tuesday and
Wednesday, and solar flux as well as sunspot numbers declined as
well.

Average solar flux for the reporting week, which runs Thursday
through Wednesday, was down over 50 points to 148.6 compared to the
previous week. Average sunspot numbers were down over 90 points to
135.6.

For this weekend expect more active geomagnetic conditions,
beginning today. Predicted planetary A index for Friday through
Sunday is 25, 25 and 18, and the expected solar flux for those days
is 130, 130 and 125. Solar flux is expected to continue low through
the first of February, then rise above 130 by February 3, above 160
by February 6, above 190 by February 9, and peak near 205 around
February 11 or 12.

Following this, solar flux is expected to bottom out again for the
short term around 135 from February 23-28. For most of February,
expect quiet geomagnetic conditions, except for unsettled conditions
around February 1, 7, and 25-27, and active conditions around
February 23-24.

K0SR, who lives in the Minneapolis area sent an email this week with
some observations on propagation from the 45th parallel. He notices
that when the K index goes above 3, he hears next to nothing on HF,
except domestic stations to the south working DX. He has also
noticed on pictures from space of aurora that there is frequently a
finger pointing down over his QTH. The author of this bulletin has
also noticed the north-south discrepancy in HF propagation. Seattle
is over 2-1/2 degrees north of Minneapolis in terms of latitude, and
K7ZR has frequently referred to local hams in a DX bulletin column
as ''Suffering Sevens.''

K0SR writes: ''When conditions are unsettled, the bands actually go
in the tank during the greyline. It is a good indication that
something bad is happening when signals disappear at sunrise/sunset,
and then come back a little bit an hour later. This happens much
more often than greyline enhancement does, and is apparent on all
bands.

If you look at the sunrise/sunset times over a given path, we
sometimes see a peak in propagation at the ''maximum dark'' time, for
example the midpoint between our sunset and European dawn. This is
frequently the best opening of the night. It isn't unusual to have
our best low band opening at 0300z, and hear nothing at European
dawn''.

Sunspot numbers for January 20 through 26 were 119, 144, 126, 135,
133, 141 and 151 with a mean of 135.6. 10.7 cm flux was 170.7,
159.3, 150.6, 140.5, 140.7, 137.4 and 140.7, with a mean of 148.6,
and estimated planetary A indices were 12, 3, 19, 25, 17, 7 and 7,
with a mean of 12.9.

Here are some path projections comparing Minneapolis, Minnesota to
Houston, Texas for this weekend when the geomagnetic field should
have a negative effect on propagation from northern latitudes.

From Minneapolis to Germany, 80 meters 2100-0930z (best 0130-0630z),
40 meters 1900-1130z (best 2330-0700z) 30 meters 1730-0830z (best
2300-0730z), 20 meters 1400-1900z, 17 meters 1600-1700z.

From Houston to Germany, 80 meters 2330-0830z, 40 meters 2200-
1030z, 30 meters 2130-1030z, 20 meters 1330-1900z, 17 meters
1400-1830z, 15 meters 1430-1730z, 12 meters 1530-1700z.

From Minneapolis to Asiatic Russia (UA9), 80 meters2230-1430z, 40
meters 2030-1600z, 30 meters 0230-2330z, 20 meters 1730-1930z and
0500-0600z.

From Houston to Asiatic Russia (UA9), 80 meters 2330-1300z, 40
meters 2230-1400z, 30 meters 2130-0530z and 0730-1500z, 20 meters
1400-1500z and 1800-1900z.

From Minneapolis to Brazil, 80 meters 2330-1000z, 40 meters
2230-1030z, 30 meters 2230-1030z, 20 meters 2030-0130z, 0300-0430z,
and 0600-0730z, 17 meters 1330-0030z, 15 meters 1400-2230z, 12
meters 1500-2130z, 10 meters 1530-2100z.

From Houston to Brazil, 80 meters2330-1030z, 40 meters 2300-1100z,
30 meters 2230-1130z, 20 meters 1930-0800z, 17 meters 1330-0100z, 15
meters 1300-0030z, 12 meters 1330-0000z, 10 meters 1400-2300z.
NNNN
/EX