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The K7RA Solar Update
SEATTLE, WA, Aug 20, 2004--Solar flux and sunspot numbers
rose this week, with August 13 and 14 being peak days for both. With low,
stable geomagnetic indices, HF conditions were good, and there were no 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. From a right angle, the mass
thrown off the sun from this region is more visible than if the spot were
facing us, however. Right now Sunspot 652 is pointed in our direction, and some
spots have been 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. Expected planetary A index for August 20-23 is
15, 12, 10 and 12. 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 has been over the past few years,
but should be better overall for the higher bands than this summer has been.
For more information concerning propagation and an explanation
of the numbers used in this bulletin see the ARRL Technical Information Service
Propagation page.
Sunspot numbers for August 12 through 18 were 140, 160,
111, 98, 68, 63 and 53, with a mean of 99. The 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.
Amateur solar observer Tad Cook, K7RA, Seattle, Washington,
provides this weekly report on solar conditions and propagation. This report
also is available via W1AW every Frida,y and an abbreviated version also
appears in The ARRL Letter.
Readers may contact the author via e-mail.
Page last modified: 10:54 AM, 20 Aug 2004 ET
Page author: awextra@arrl.org
Copyright © 2004, American Radio Relay League, Inc. All Rights Reserved.
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