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The K7RA Solar Update
SEATTLE, WA, Mar 4, 2005--This
week saw a quiet sun, which will be a frequent observation over the
next few years. The average daily sunspot number was down nearly 31
points to 14.9, and average daily solar flux was off 21 points to
76.3. Planetary geomagnetic activity was down just slightly, and
mid-latitude activity was just about the same as the previous
reporting week.
Unsettled to active geomagnetic
conditions were expected during last weekend (February 26-27), due to
a strong solar wind. As it turned out, the only day with even
slightly unsettled conditions was Monday--the last day of
February, and any activity was brief. All week the Interplanetary
Magnetic Field (IMF) pointed north, which shielded Earth from any
solar wind. The sun was blank most of the week, with only small
Sunspot 739 transiting across the visible solar disk.
The spaceweather.com Web site has
a review
of the IMF Check and how it can affect geomagnetic stability. There’s
more
about IMF on the Windows to the Universe Web site.
Thanks to Jon Jones, N0JK, for passing along this information.
Over the next week expect a rising
sunspot count and solar flux, with flux values peaking above 100
around March 11-14. March 6-9 could see some unsettled to active
geomagnetic conditions based on activity during the previous solar
rotation.
This weekend is the ARRL
International DX SSB Contest. Don’t expect great conditions
like when the sunspot cycle was higher, but at least we are moving
toward the spring equinox and the geomagnetic conditions should be
quiet.
Last week’s “Solar
Update” stimulated some questions about resources for
understanding sporadic-E propagation. The ARRL Propagation
page includes a two-part article, “Sporadic-E--A Mystery
Solved?” (scroll down to the “Articles” section).
You must be an ARRL member and be registered and logged into the ARRL
Web site to access these articles. Visit the ARRL Technical
Information Service Propagation
page for more information concerning propagation and an explanation
of the numbers used in each week’s “Solar Update.”
Sunspot numbers for February 24
through March 2 were 17, 15, 27, 12, 11, 11 and 11, with a mean of
14.9. The 10.7 cm flux was 80.3, 78.2, 76.6, 75.8, 75, 73.7 and 74.6,
with a mean of 76.3. Estimated planetary A indices were 5, 9, 9, 8,
12, 11 and 12 with a mean of 9.4. Estimated mid-latitude A indices
were 4, 9, 9, 6, 8, 10 and 8, with a mean of 6.6.
- 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 appears in The
ARRL Letter. Readers may contact the author via
e-mail.
-
Page last modified: 10:48 AM, 04 Mar 2005 ET
Page author: awextra@arrl.org
Copyright © 2005, American Radio Relay League, Inc. All Rights Reserved.
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