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ARRL Propagation Bulletin ARLP001 (2001)

ARLP001 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 1  ARLP001
From Tad Cook, K7VVV
Seattle, WA  January 5, 2001
To all radio amateurs 

ARLP001 Propagation de K7VVV

On January 2 and 3 a large sunspot group, number 9289, crossed the
center of the visible solar disk. This is the area that has the
greatest effect on the earth. It covered 890 millionths of the solar
disk, which is an area five times the surface of the earth. On
January 4 around 0900z the earth reached perihelion, which is the
closest it will be to the sun all year. Sunlight at perihelion is
about 7 percent more intense over the whole of the earth than it is
in July.

KD5MSW sent reminders of a couple of sites for viewing the sun. One
is a live real time image of the sun at The other, at gives movies of
the sun taken from satellites.

Sunspot numbers and solar flux were down over the past week, with
the weekly average sunspot number off over 20 points and the average
solar flux declining nearly 14. Geomagnetic conditions were very
quiet, with Wednesday having only moderately unsettled conditions,
with a planetary A index of 11. The high-latitude College A Index in
Fairbanks, Alaska was 22 on that day, but the day before it was
actually 0. This is unusually low, especially for such a high
latitude location where any solar event aimed toward earth seems to
cause upset and absorption for polar HF signals. The College K index
was also 0 for each 3-hour period, except for the last period of the
UTC day, when it was 1.

Solar flux is expected to continue to fall over the next few days,
and reach a short term minimum around January 9 or 10. The next
solar flux peak is expected around January 18-21. Unsettled
geomagnetic conditions are expected with a planetary A index of 15
for January 5 and 6, stabilizing slightly to an A of 12 for January
7 and 8.

Now as promised in last week's bulletin, it is time to review the
numbers for last year, and perhaps divine when the peak of this
sunspot cycle occurred.

The yearly averages of daily sunspot numbers for 1995-2000 were
28.7, 13.2, 30.7, 88.7, 136.3 and 174.4. The yearly averages of
daily solar flux numbers for 1995-2000 were 77.1, 73.4, 81, 117.9,
153.7 and 181.2. We can see that the minimum activity was centered
around 1996 and that the maximum was in 2000.

If you use WA4TTK's solar plotting software with the data from these
bulletins, you can see from the chart that there were a couple of
high points in activity this year. The first was May 17 when the
solar flux was 262 and sunspot number 342. The second was July
18-20, when sunspot numbers were 343, 342 and 401 and solar flux was
261.9, 249.9 and 252.9. Examination of the graph shows a general
drop in activity since July. (If you don't have the solar plotting
software, you can get it for free from WA4TTK's web site at or specifically Note that you can also download
an updated data file, which has all of the solar flux and sunspot
data from this bulletin from January 1, 1989 through December 31,

These peaks suggest a solar maximum around May or July. Since there
is so much daily variation in the data (even at the cycle peak), it
is useful to look at averages. The monthly averages of daily sunspot
numbers for 2000, January through December, were 140.8, 161.9,
203.6, 193.4, 188.8, 190.3, 236.7, 166.7, 169.9, 138.9, 149.9 and
146.4. The 236.7 number for July was the highest for the year.
Monthly Average of daily solar flux for the year was 159, 174.1,
208.2, 184.2, 184.5, 179.8, 200.5, 163.1, 201.7, 167.7, 178.8 and
173.6. This gives us three peaks, in March, July and September. The
quarterly daily sunspot averages were 168.9, 190.8, 193.1 and 145,
and quarterly solar flux was 180.5, 182.9, 188.3 and 173.3. These
suggest a maximum in the third quarter, July through September.

Ultimately the solar physicists who represent the real scientific
expertise will come up with an approximate date for the peak using a
smoothed moving average, but the data is not all here yet.

Contests this weekend include the ARRL RTTY Roundup and the Low Band
CW portion of the Japan International DX Contest. Since this
involves working Japanese stations only and only on 160, 80 and 40
meters, below are some path projections to Japan. We have not
attempted 160 meter path projections in the past, but here is an
attempt. 160 meter operators may email observations to the author at

From Seattle, 160 meters 0800-1600z, 80 meters 0730-1730z, 40 meters
0600-1900z. From San Francisco, 160 meters 0700-0600z, 80 meters
0630-1630z, 40 meters 0600-1730z. From Los Angeles, 160 meters
0700-1600z, 80 meters 0630-1600z, 40 meters 0530-1700. From Hawaii,
160 meters 0730-1800z, 80 meters 0700-1830z, 40 meters 0600-1930z.
From Salt Lake City, 160 meters 0730-1530z, 80 meters 0700-1600z, 40
meters 0600-1730z. From Arizona, 160 meters 0730z-1500z, 80 meters
0700-1530z, 40 meters 0530-1630z. From Dallas, 160 meters
0730-1430z, 80 meters 0630-1430z, 40 meters 0700-1500z. From the
center of the continental U.S., 160 meters 0730-1430z, 80 meters
0700-1500z, 40 meters 0530-1700z. From Atlanta, 160 meters
0800-1300z, 80 meters 0700-1330z, 40 meters 0700-1400z. From
Philadelphia, 160 meters 0800-1230z, 80 meters 0700-1400z, 40 meters
0530-1430z. From Chicago, 160 meters 0730-1330z, 80 meters
0700-1430z, 40 meters around 0600z and 0700-1630z. From Cleveland,
160 meters 0730-1300z, 80 meters 0700-1430z, 40 meters 0530-1500z.
From Boston, 160 meters 0800-1200z, 80 meters 0700-1400z, 40 meters

Sunspot numbers for December 28 through January 3 were 159, 150,
140, 153, 119, 143 and 128 with a mean of 141.7. 10.7 cm flux was
185.4, 181.5, 182.1, 169.5, 171, 176.1 and 169.9, with a mean of
176.5, and estimated planetary A indices were 5, 6, 2, 2, 3, 4 and
11 with a mean of 4.7.


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