The
K7RA Solar Update
SEATTLE, WA, Apr 25, 2003--Sunspot numbers
and solar flux rose over the past week. Average daily sunspot numbers were up
more than 44 points to 100.4, and solar flux was nearly 17 points higher to
118.6. Solar wind and the resulting geomagnetic instability that has been
prevalent for the past few weeks continued, and is expected to last at least
through this weekend.
The current outlook has the Friday through
Monday planetary A index for April 25-28 at 20, 25, 25 and 20. Current projections
forecast quiet conditions (where the A index is 10 or lower) for May 3-5, but
higher just before that period and for nearly two weeks following. This is
because of coronal holes rotating into view from April 29 through May 2 and
again May 6-8. A large coronal hole should return around May 12.
The reason for the unsettled to active
geomagnetic forecast for this weekend is because of an ongoing solar wind, and
an active sunspot that released two solar flares on April 23. This was not
squarely directed at Earth, but could cause some mischief today. The most
active days recently were April 16-17, when planetary A indices were 31 and 30
and the K index went as high as 6. Over those same two days the higher latitude
college A index (measured in Alaska) was 54 and 50, and the K index went to 7,
indicating a severe geomagnetic storm.
Predicted solar flux is 128 and 130 for
Friday and Saturday, April 25-26, and then around 135 through the next week.
When the sun shows some spots and geomagnetic indices are quiet, this is when
HF conditions are most promising. But lately with the decline in the solar
cycle, there haven't been many sunspots but there have been enough flares and
coronal holes to keep conditions unstable. Current projections show this cycle
hitting minimum around the end of 2006 and the beginning of 2007. A few years
after that we should be back to where we are now (in terms of sunspots and
solar flux) and on the rise again.
For more information about propagation and an
explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site.
Sunspot numbers for April 17 through 23 were
37, 51, 69, 93, 154, 147 and 152, with a mean of 100.4. The 10.7-cm flux was
101, 107.8, 112.1, 118.5, 125.8, 132.4 and 132.8 with a mean of 118.6.
Estimated planetary A indices were 30, 20, 18, 16, 21, 22 and 18, with a mean
of 20.7.
Many thanks to Carl Luetzelschwab, K9LA, for
filling in for me last week.
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 Friday and an abbreviated version
also appears in The
ARRL Letter. Readers may contact the author via k7ra@arrl.net.
Page last modified: 10:37 AM, 25 Apr 2003 ET
Page author: awextra@arrl.org
Copyright © 2003, American Radio Relay League, Inc. All Rights Reserved.
![Previous (earlier) Story](/images/sty-down.gif ""Broadband Over Power Line" Could Pose HF Interference Threat"){kind=small}
Previous: "Broadband Over Power Line" Could Pose HF Interference Threat
Next: FCC Alleges Michigan Ham Engaged in Deliberate Interference, Made Threats
