ARRL

ARRL Propagation Bulletin ARLP019 (2003)

SB PROP @ ARL $ARLP019
ARLP019 Propagation de K7RA

ZCZC AP19
QST de W1AW  
Propagation Forecast Bulletin 19  ARLP019
From Tad Cook, K7RA
Seattle, WA  May 9, 2003
To all radio amateurs 

SB PROP ARL ARLP019
ARLP019 Propagation de K7RA

The weeks of active geomagnetic conditions continue and seem to
stretch into months. This week was no exception. The average
planetary A index was 20.7, and the week before was 23.7. One day
was quiet, May 4, when the planetary A index was only 7. The worst
days this week were May 1 when the A index was 40 and May 7 when it
was 36.

These were the worst days for HF operators, but probably not if you
like 6-meters. John Reynolds, N7QF reported from Utah that on May 1
he had a good sporadic-E opening into Oklahoma and Texas. He didn't
say, but I assume this was on 6-meters. The distance was about 850
miles, and he said most of the people he worked were using 100 watts
and a 3 element Yagi.

April 30, the day prior, had Jon Jones, N0JK working Argentina on
6-meters from Kansas with E and F2 layer propagation. He says he
also worked TI5KD with double-hop E-skip.

Solar flux and sunspot numbers were down this week. Average sunspot
numbers were down nearly 40 points from the previous week and
average solar flux was down over 10 points. Solar flux and sunspot
numbers have been declining again. Solar flux will probably go below
100 over the weekend. Solar flux was below 100 only one day in the
past month on April 17, but it dipped just one point below to 99.

Predicted solar flux for Friday, May 9 to Monday, May 12 is 95, 95,
100 and 100. The latest forecast shows the planetary A index not
going below 20 until May 16. The earth is currently inside a solar
wind stream, as it often has been for past months. An interplanetary
shock wave, probably from a coronal mass hit earth at 0500z today,
May 9, and should keep conditions active.

Nearly ten years ago Scott Craig, WA4TTK released a freeware program
for plotting the solar numbers from this bulletin. He calls it the
Solar Data Plotting Utility, and it has been improved over the
years. The current version runs in Windows and can automatically
retrieve data, either from this bulletin, or via FTP from the ARRL.
Scott has just posted a new updated data file that has daily solar
flux and sunspot numbers from January 1, 1989 through April 30,
2003. You can download Scott's software from
http://www.craigcentral.com .

Another great resource is the NOAA Space Environment Center's
Preliminary Report and forecast, which comes out weekly. It used to
be published on paper and mailed, but you can look at it in PDF form
at the SEC NOAA we site at,
http://www.sec.noaa.gov/weekly/index.html .

The current issue, published May 6, has some tables showing
predicted solar flux and sunspot numbers until the end of 2007, and
smoothed numbers back to January 1998. It looks like currently we
have solar activity around the same level as it was about 5 years
ago. Of course a big difference is that back then the solar activity
was increasing, and now it is on the decline. The chart seems to
suggest that in 14 months the sunspot count will be about half what
it is now, and it drops to one fourth about 2 years and one month
from now.

For more information on propagation and an explanation of the
numbers used in this bulletin see the Propagation page on the ARRL
Web site at http://www.arrl.org/tis/info/propagation.html .

Sunspot numbers for May 1 through 7 were 171, 175, 134, 172, 144,
117, and 109, with a mean of 146. 10.7 cm flux was 148.7, 156.5,
147.7, 142, 128.8, 122, and 110.2 with a mean of 136.6. Estimated
planetary A indices were 40, 17, 10, 7, 12, 23, and 36, with a mean
of 20.7.
NNNN
/EX