The K7RA Solar Update
SEATTLE, WA, Jul 30, 2004--Sunspot 652 has rotated out of
view, but it was the source of major excitement this week. Coronal mass
ejections caused big geomagnetic storms on Sunday and Tuesday, July 25 and 27. The
planetary A index was 122 on Sunday, 31 the next day and 162 on Tuesday. This
caused radio blackouts on the HF bands, but it provided some excitement for
6-meter operators who reported great openings. The activity was enhanced by a
south-pointing interplanetary magnetic field, leaving the Earth vulnerable to
blasts of energy from the sun.
Auroral displays accompany periods of high geomagnetic
activity, but they tend to predominate at higher latitudes. The stronger the
activity, the higher the K and A index and the further south that northern
lights can be seen. We're used to seeing photos of aurora from Alaska,
especially above the Arctic Circle, but the Science@NASA
site displays a photo taken July 27 at Borrego Springs, California--just 20
miles north of the 33rd parallel in Southern California.
Marc Weinberg, K9PET, sent a note about being maritime
mobile in Svalbard as JW/K9PET last week. He was north of the 79th parallel,
and when geomagnetic disturbances hit, he said he "thought the world had
disappeared." The Lindblad Expeditions site includes a photo--taken
from a distance--of his Amateur Radio operation on land from Raudfjorden
Spitsbergen on July 20. In a few weeks, K9PET expects to post additional photos
on his own Web site.
ARRL Lab Test Engineer Mike Tracy, KC1SX, let me know
about an interesting link for a Macromedia Flash movie, HF Propagation Primer, by AE4RV.
Over the next few days expect unsettled to active
geomagnetic conditions, and declining sunspot and solar flux numbers. Predicted
planetary A index for Friday through Monday, July 30 through August 2, is 30,
20, 20 and 8. Predicted solar flux for the same period is 95, 90, 85 and 90. Solar
flux is expected to peak again at about 125 around August 14-18. More sunspot
activity is ahead, at least for the near term.
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 July 22 through 28 were 117, 86, 109,
130, 113, 66 and 66, with a mean of 98.1. The 10.7 cm flux was 172.9, 165.1,
147.2, 156.2, 128, 118.1 and 100.7, with a mean of 141.2. Estimated planetary A
indices were 19, 47, 27, 122, 31, 162 and 14, with a mean of 60.3. Estimated
mid-latitude A indices were 13, 21, 29, 64, 26, 119 and 11, with a mean of
40.4.
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: 10:36 AM, 30 Jul 2004 ET
Page author: awextra@arrl.org
Copyright © 2004, American Radio Relay League, Inc. All Rights Reserved.
Previous: Nevada Fires Make July a Busy Time for ARES Volunteers
Next: Amateur Radio Facilitates Dramatic Rescue at Sea
