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04 August, 2007
Average daily sunspot numbers rose very little this week, less than 6
points to 7.3. There were no major geomagnetic upsets, only slightly unsettled
conditions on the first day of August.
We saw eight straight days of no sunspots, then a spot or two over four
days, then no spots on the first two days of August. A week from now,
August 10, we may see the beginning of several days with a few sunspots
every day. Expect unsettled geomagnetic conditions centered on August
7 and again on August 10.
Geophysical Institute Prague predicts quiet conditions August 3-5, quiet
to unsettled August 6, unsettled to active August 7, and back to quiet
August 8-9.
There were six and two meter reports this week. On Sunday, July 29 Dick
Bingham, W7WKR, who lives in the very remote mountain village of Stehekin,
Washington (reached by boat) reports that he began hearing six meter beacons
around 1800z, and until 2300z he worked 22 grids, including HR9BFS in
EK66 (Honduras) as well as WA/CA/ID/MT/CO/TX/UT. Dick is blocked by a
high ridge running northwest to southeast, with takeoff elevations in
excess of 25 degrees, so he doesn't hear the northeastern United States
and Canada.
WB4SLM reported interesting E-skip on 2 meters, and from EM82 he worked
EM14, EM15 and EM25, all around 2100z on Sunday. He lives in Georgia,
and during a 30 meter QSO with his father, W9JNH in Texas, around 2133-2135z
he heard long delayed echoes on his CW signal.
Four days earlier on June 25, Roger Lapthorn, G3XBM reported his best
6-meter DX ever when he worked K1TOL in Maine on CW. Roger was running
just a few watts into a vertical mounted on the side of his house. Roger
says the distance was over 5000 kilometers.
With July over, we can spin some numbers and look for trends.
Monthly averages of daily sunspot numbers for April 2006 through July
2007 were 55.2, 39.6, 24.4, 22.6, 22.8, 25.2, 14.7, 31.5, 22.2, 28.2,
17.3, 9.8, 6.9, 19.8, 20.7 and 15.6. Monthly averages of daily solar flux
for the same period were 88.9, 80.9, 76.5, 75.8, 79, 77.8, 74.3, 86.3,
84.4, 83.5, 77.7, 72.2, 72.4, 74.4, 73.7 and
71.6.
Looking at 3-month smoothed sunspot numbers, now the July numbers we
can add to May and June to show the three-month average centered on June.
These numbers are based on data from the past 21 months, November 2005
through July 2007:
Dec 05 40.6
Jan 06 32.4
Feb 06 18.1
Mar 06 27.7
Apr 06 38.5
May 06 39.7
Jun 06 28.9
Jul 06 23.3
Aug 06 23.5
Sep 06 21.2
Oct 06 24.1
Nov 06 23.1
Dec 06 27.3
Jan 07 22.7
Feb 07 18.5
Mar 07 11.2
Apr 07 12.2
May 07 15.8
Jun 07 18.7
These numbers are calculated like this: April 1 through June 30 is 91
days. Add all the daily sunspot numbers over those three months, then
divide by 91, and the result is approximately 15.8, centered on May, the
middle month. Likewise, May 1 through July 31 has 92 days, and the sum
of daily sunspot numbers over that period divided by 92 is 18.7.
If the average of daily sunspot numbers for the 31 days of August turns
out to be more than 20 (meaning the sum of all the sunspot numbers for
the month exceeds 620), we should see the three-month average centered
on July rise above the June average. We will see that result in ARLP037,
on September 7.
This 3-month moving average of sunspot numbers is turning out to be a
nice indicator of cycle trends, with the average smoothly declining from
December through March, and increasing since. We'll know some day, perhaps
in a year or two, if the low number in March is a good indicator of cycle
minimum or not. Users of Scott Craig's Solar Data Plotting Utility (available
free from http://www.craigcentral.com/sol.asp)
may have noticed that this cycle minimum so far doesn't look as long as
the previous minimum around 1995-1997. But of course, if we are at the
minimum or just passed it, then we are only looking at probably half of
its eventual length on the graph. I hope the upturn comes soon, and is
dramatic.
If you would like to make a comment or have a tip for our readers, email
the author at, k7ra@arrl.net .
For more information concerning radio propagation, see the ARRL Technical
Information Service at
http://www.arrl.org/tis/info/propagation.html.
For a detailed explanation of the numbers used in this bulletin, see
http://www.arrl.org/tis/info/k9la-prop.html
.
An archive of past propagation bulletins is at http://www.arrl.org/w1aw/prop/.
Monthly propagation charts between four USA regions and twelve overseas
locations are at http://www.arrl.org/qst/propcharts/.
Sunspot numbers for July 26 through August 1 were 0, 0, 13, 14, 13, 11
and 0 with a mean of 7.3. 10.7 cm flux was 68.4, 68.7, 69.9, 69, 68.9,
68, and 68.8, with a mean of 68.8. Estimated planetary A indices were
9, 8, 4, 14, 10, 6 and 17 with a mean of 9.7. Estimated mid-latitude A
indices were 6, 6, 3, 11, 10, 4 and 15, with a mean of 7.9.
Source: The
American Radio Relay League
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reports can be found at:
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