ARRL

ARRL Propagation Bulletin ARLP015 (2000)

SB PROP @ ARL $ARLP015
ARLP015 Propagation de K7VVV

ZCZC AP15
QST de W1AW  
Propagation Forecast Bulletin 15  ARLP015
From Tad Cook, K7VVV
Seattle, WA  April 14, 2000
To all radio amateurs 

SB PROP ARL ARLP015
ARLP015 Propagation de K7VVV

Solar activity was down over the past week. Average solar flux was
off over 35 points and average sunspot numbers were down over 80
points, when compared with the previous week. Geomagnetic indices
were way up at the beginning of the reporting week, with major
storms on April 6 and 7 when the planetary A indices were 56 and 50.
As the UTC day passed from Thursday to Friday, the K index was as
high as 8, which is very disturbed.

N7GXD reported from Northern Utah that he worked a number of
stations some distance away, including Colorado and Canada, on 6
meters using only 10 watts into a single quad loop. This was
enhanced by aurora propagation on Thursday evening. You can read the
MSNBC story on this aurora on the web at
http://www.msnbc.com/news/392145.asp?0a=2347151.

Solar flux should reach a short-term minimum in the next few days.
The predicted solar flux values for Friday through Tuesday are 165,
165, 160, 160 and 165. Flux values are expected to reach 200 by
April 21, and peak near 225 around April 27. Predicted planetary A
indices for the next five days are 10, 12, 7, 7 and 8. After this
weekend the A index should stay in the single digits until April 26
through May 4, with a peak in unsettled to active geomagnetic
conditions around April 29.

With somewhat lower solar flux and the passing of the spring
equinox, the author has noted that 10 meter conditions may not be
what they were a short time ago. As an example, on March 22, the
solar flux at noon at the Penticton observatory was 233.8. Run these
numbers in a popular propagation program, and it shows a strong path
from Seattle to Hawaii on 10 meters, with good signals from
1800-0400z. But run the numbers for April 13, when the flux was 164,
and the numbers are quite different. Now it shows an unreliable path
covering the same period, but with much less chance of an opening.

If we pretend that April 13 had the higher solar flux of 233.8, the
path does get more reliable, but nothing like the path right around
the equinox. There is the possibility of a longer lasting opening on
April 13, because there are more hours of daylight. If we run the
numbers for a day right in between the two dates, which is April 2,
we see values somewhere in between the two. The big difference is
seasonal effects. For 10 meters, there is really no time like the
equinox at the solar cycle peak for fabulous conditions.

Email received from several readers pointed out a couple of errors
in the last bulletin, ARLP014. An unfortunate accident with a search
and replace function changed every appearance of the number 10 to
say 10 meters. Not all of these errors were caught and edited. VE3YE
pointed out that the reference to solar flux of 343 on November 10
should have said sunspot number. Oh, if only the solar flux were
that high.

If you ever have a comment, write to k7vvv@arrl.net.

Last week's bulletin also omitted a review of monthly and quarterly
solar flux numbers, which we will examine here.

The average solar flux for the four quarters of 1999 were 136.7,
145, 157.6 and 175.2 . The value for the first quarter of 2000 was
180.5. This indicates the sort of upward progression expected as we
move toward the peak of cycle 23. The average monthly solar flux for
January through March was 159, 174.1 and 208.2, also a nice upward
trend.

Sunspot numbers for April 6 through 12 were 155, 172, 167, 160, 175,
148 and 172 with a mean of 164.1. 10.7 cm flux was 177.7, 174.9,
182, 176.3, 177.8, 181.5 and 173, with a mean of 177.6, and
estimated planetary A indices were 56, 50, 14, 13, 20, 10 and 5,
with a mean of 24.

The path projections for this weekend are from Ohio.

To Europe, 80 meters 0000-0600z, 40 meters 2230-0700z, 30 meters
2130-0630z, 20 meters 1930-0300z, 17 meters 1100-0130z, 15 meters
1330-0000z, 12 meters and 10 meters 1700-2000z.

To Southern Africa, 80 meters 0000-0430z, 40 meters 2300-0500z, 30
meters 2200-0530z, 20 meters 2130-0530z, 17 meters 2030-0200z, 15
meters 2030-0130z, 12 meters 1900-0000z, 10 meters possibly
1800-2200z.

To South America, 80 meters 0000-0930z, 40 meters 2330-1000z, 30
meters 2300-1030z, 20 meters 2130-0630z, 17 meters 2100-0500z, 15
meters 1130-1330z and 2000-0330z, 12 meters 1300-2330z, 10 meters
1600-2100z.

To the Caribbean, 80 meters 2330-1030z, 40 meters 2200-1200z, 30
meters open all hours, strongest 0030-0930z, weakest 1530-1800z, 20
meters open all hours, best 0030-0630z, weakest 1500-1830z and
0700-0800z, 17 meters 1000-1400z and 1700-0500z, 15 meters
1100-0400z, 12 meters 1230-0200z, 10 meters 1500-2130z.

To Australia, 80 meters 0900-1130z, 40 meters 0830-1200z, 30 meters
0730-1230z, 20 meters 0700-0800z and 1030-1300z, 17 meters
1200-1330z, 15 meters 1330-1430z.

To Japan, 80 meters 1000-1100z, 40 meters 0900-1130z, 20 meters
0830-1200z, 17 meters 1230-1430z, 15 meters 1930-0330z, 12 meters
2030-0000z, 10 meters possibly 2030-2200z.
NNNN
/EX