ARRL

ARRL Propagation Bulletin ARLP040 (1998)

SB PROP @ ARL $ARLP040
ARLP040 Propagation de K7VVV

ZCZC AP40
QST de W1AW  
Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7VVV
Seattle, WA  October 2, 1998
To all radio amateurs 

SB PROP ARL ARLP040
ARLP040 Propagation de K7VVV

Solar activity was down a bit last week, with the average solar flux
off by six points and average sunspot numbers lower by almost 27
points.

Now that September is over it's time to look at some long term
trends.  The last quarter of 1997 had an average solar flux of 94.3.
The next quarter, January through March of 1998, the average flux
rose to 98.8.  The second quarter of this year the average flux was
107.8, and this last quarter the average flux was 129.2.

The average flux for September was 137.7, and for May through August
it was 106.7, 108.5, 114.1 and 136.  The average flux over this past
week was 125.6, and for the same period one year ago it was only
88.2.  We can see that the general trend in solar activity is up,
although there was only a negligible increase from August to
September.

Last week the really active geomagnetic day was on Friday, when the
planetary A index was 121 and the planetary K index went as high as
9, which signals a major geomagnetic storm.

Over the next few days, Friday through Sunday, the solar flux is
forecast to be 115, 113 and 112, and the planetary A index for the
same period is predicted at 20, 20 and 15.  Unsettled to active
conditions are predicted around October 15 and for October 18-23 as
well.  The solar flux is expected to rise after the weekend, to
above 130, then drop down to 120 around October 12-14, then peak
around 145 around October 20.  Now that we are in the fall season,
look for good HF propagation when the K and A index is low.

If you have access to the web, check NASA Space Science News at
www.astronomynews.com and look for the September 29 article under
Astrophysics titled Crusty Young Star Makes its Presence Felt.  This
is about the big gamma ray flash which blasted the earth on August
27, which was widely reported this past week in the news media.

On that day the planetary A index was 112, and it was assumed at the
time that this was caused by a proton flare from our sun about 4
days earlier.  Now some scientists are wondering if perhaps the
resulting disturbance on earth may have been enhanced by a wave of
energy from a Magnetar, or super-magnetized star about 15,000 light
years from earth.  Paul Harden, NA5N of the National Radio Astronomy
Observatory in New Mexico wants to hear from hams who may have been
listening to medium wave or HF radio around 3:22 AM Pacific Daylight
Time (1022 UTC) in the Western United States on August 27.  He can
be reached at pharden@nrao.edu.

Paul says that this is the first known event from outside our solar
system that has affected the earth's environment.  He also invites
us to look at his institution's web page on this event at
www.nrao.edu/pr/magnetar.html.  He noted that if only the SOHO
satellite had been working, meaningful measurements could have been
made which could easily separate the effects of the solar flare and
the magnetar gamma ray burst.

The October 1998 issue of the magazine Astronomy has a couple of
items of interest to solar observers.  Page 28 has a stunning
picture from the NASA Transition Region and Coronal Explorer
spacecraft showing loops of plasma from an active solar region on
April 25.  The same issue on page 60 has an article about
forecasting solar storms titled Blowin' in the Solar Wind.

Sunspot Numbers for September 24 through 30 were 156, 118, 115, 87,
127, 86 and 59 with a mean of 106.9.  10.7 cm flux was 135.4, 122.1,
126.9, 135, 122.5, 115.9 and 121.5, with a mean of 125.6, and
estimated planetary A indices were 28, 121, 14, 12, 6, 10, and 8,
with a mean of 28.4.
NNNN
/EX