Register Account

Login Help

ARRL Propagation Bulletin ARLP034 (2004)

ARLP034 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 34  ARLP034
From Tad Cook, K7RA
Seattle, WA  August 20, 2004
To all radio amateurs 

ARLP034 Propagation de K7RA

Solar flux and sunspot numbers rose this week.  August 13-14 were
the peak days for both, and with low and stable geomagnetic indices,
HF conditions were good.  There weren't any days with notable
geomagnetic upsets.

Sunspot 649 has rotated off the western limb of the sun, and on
August 18 it emitted a large coronal mass ejection.  Since it is
facing away from earth, we are not likely to be affected, but from a
right angle the mass thrown off the sun from this region is more
visible than if the spot were facing us.  Right now sunspot 652 is
pointed in our direction, and there are some spots identified on the
sun's far side using the helioseismic holography method.

Geomagnetic indices are expected to rise, then decline again over
the next few days.  The expected planetary A index for August 20-23
is 15, 12, 10 and 12.  The expected solar flux for the same days is
115, 110, 105 and 100.

We are only a month away from the Fall equinox.  Of course this will
bring the good Fall conditions to HF.  Due to the declining solar
cycle, it probably won't be as good as Fall was over the past few
years, but should be better overall for the higher bands than
summertime was.

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at,

Sunspot numbers for August 12 through 18 were 140, 160, 111, 98, 68,
63 and 53 with a mean of 99.  10.7 cm flux was 147.2, 148.6, 149.2,
138.8, 133.6, 135 and 139.9, with a mean of 141.8.  Estimated
planetary A indices were 9, 9, 9, 7, 8, 11 and 13, with a mean of
9.4.  Estimated mid-latitude A indices were 6, 5, 6, 3, 5, 9 and 10,
with a mean of 6.3.


Instragram     Facebook     Twitter     YouTube     LinkedIn