ARRL

ARRL Propagation Bulletin ARLP001 (2013)

SB PROP @ ARL $ARLP001
ARLP001 Propagation de K7RA

ZCZC AP01
QST de W1AW  
Propagation Forecast Bulletin 1  ARLP001
From Tad Cook, K7RA
Seattle, WA  January 4, 2013
To all radio amateurs 

SB PROP ARL ARLP001
ARLP001 Propagation de K7RA

The New Year brings dreams of solar cycles of old, so distant now,
sweetly remembered for their profusion of sunspots. We hear many
times from operators who began in the amateur radio service as
teenagers at the peak of Cycle 19. With youthful optimism, they
naturally assumed that radio propagation would always be like that,
when a few watts and a modest radiator on 10 meters spanned the
globe during all the days and nights.

If you were age 13 to 17 in 1957 to 1959, the peak of Cycle 19,
perhaps you were born between 1941 and 1945, and probably looked
forward to the next peak in activity. That may have been a
disappointment when Cycle 20 peaked around 1969, as that had a
somewhat broader peak but at a far lower level. You can see it
graphically at http://wm7d.net/hamradio/solar/historical.shtml.
These young adults, now 24 to 28 years old in 1969, might be busy
starting families and careers, and no doubt fondly recalling simpler
times and the tremendous propagation of their younger years.

Cycle 21 peaked around 1980, and the former teenaged ham of Cycle 19
was now 35 to 39 years old. This was quite an improvement over the
last cycle, as was Cycle 22, which looked like an echo of Cycle 21.
Cycle 22 peaked around 1991-1992, with a more pronounced
double-peak. The former teenager was now 47 to 51 years old, solidly
into middle-age, and still wondering if sunspot activity would ever
roar back to the levels of the late-1950s.

The following cycle, number 23, was another double-peak, but
significantly lower in 2000 to 2002 than the previous cycle. Perhaps
another disappointment for the now 56 to 60 year old ham, who then
sees solar activity slide into a long and low minimum over the next
decade, impossible to imagine 60 years earlier. The 160 meter
operators, quite happy in this situation with a much quieter Sun,
have no such longing for the active Sun of yesteryear.

Now the young ham of the late 1950s contemplates the peak of Cycle
24, apparently much lower than any seen in most of the past century,
and expected to grow to maximum this year. Now we have many more
tools to observe and measure both solar activity and propagation,
and we know that activity could still increase significantly. Some
foresee decades of lower activity, but of course predicting future
solar activity is a very tricky proposition, and anything could
happen.

At
http://www.solen.info/solar/images/comparison_recent_cycles.png
you can see a comparison of recent cycles, from 21 to the current
24.

While we've seen a number of papers and predictions for a series of
quieter sunspot cycles, some disagree. For instance, Michael
Proctor, professor of Astrophysical Fluid Dynamics at Cambridge
University is not convinced. He was quoted this year as saying,
"This present cycle is similar to the weak one that ended in 1913,
and that was followed by a strong cycle."

Those were Cycles 14 and 15, and Cycle 15 was only strong relative
to 14. Cycles 17, 18 and 19 were stronger than 15, and so were 21,
22 and 23.

It is also important to remember there is wild variability in solar
activity. To make those graphs of sunspot numbers appear smooth,
each point on the graph actually represents an average of a year of
data. When averaged, the flurry of solar activity at the end of 2011
and some future activity in 2013 could appear as a broad peak on a
graph.

NASA looks frequently at their predictions for the current cycle,
and often adjusts them every month. The latest shows a smoothed
sunspot number a bit lower than the forecast from several weeks ago.
In the December 10 forecast they predicted a smoothed sunspot number
of 72 in the late in 2013, but that number is now 69 in the January
2 release. Note these are the lower international sunspot numbers,
which are always less than Boulder numbers presented in this
bulletin. Read the report at
http://solarscience.msfc.nasa.gov/predict.shtml.

With the change from 2012 to 2013, now is a good time to review
sunspot numbers and trends. Average daily sunspot numbers in 2013
were up substantially from 2012. From 2004 through 2012 the yearly
progression was 68.6, 48.9, 26.1, 12.8, 4.7, 5.1, 25.5, 29.9 and
82.3. I took all the daily sunspot numbers for 2012, added them
together, and the sum was 30,133. Divide that by 366 (the number of
days in 2012, a leap year) and the result is approximately 82.3. In
2011 it was 10,913 divided by 365, yielding 29.9.

The 2012 average was higher than any year after 2003. But at the
peak of Cycle 23, the averages from 1998 to 2003 were all higher:
88.7, 136.3, 173, 170.3, 176.7, and 109.2. It seems unlikely that
average daily sunspot numbers this year will reach anywhere near the
level of 2000-2002.

We observe a moving 3-month average of sunspot numbers, in an
attempt to smooth out some of the variations. Unfortunately, the
past three months were much lower then the three month period ending
one month earlier. The current average of 74.4, centered on November
2012, is lower than any three month period since averages centered
on February and March of 2012.

The 3 month period previous to the current one is centered on
October 2012, and covers September through November. The average
then was 82.3. To recap averages from previous bulletins, the
three-month moving averages of daily sunspot numbers centered on
July 2011 through November 2012 were 63, 79.6, 98.6, 118.8, 118.6,
110, 83.3, 73.7, 71.2, 87.3, 91.5, 96.5, 91.9, 89.9, 81.2, 82.3, and
74.4.

Looking at the past week, yesterday we saw a sizable gain in solar
flux, when the value went from 106.7, 113.6, 117.8, and 119 to
128.8, on December 30 through January 3. NOAA and USAF predict solar
flux at 130 on January 4-6, 125 and 120 on January 7-8, 115 on
January 9-10, 110 on January 11, 105 on January 12-13, 110 on
January 14-17, 115 on January 18-20, and 120 on January 21-23.

Predicted planetary A index is 5 on January 4-12, 10 on January 13,
5 on January 14-25 and 8 on January 26.

F.K. Janda, OK1HH issues a weekly geomagnetic forecast. This week he
says geomagnetic conditions will be quiet January 4, quiet to active
January 5, mostly quite January 6, quiet January 7-9, quiet to
unsettled January 10-12, active to disturbed January 13, quiet to
unsettled January 14-16, quiet January 17-19, mostly quiet January
20-21, and quiet on January 22-26.

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 web page at
http://arrl.org/propagation-of-rf-signals. For an explanation of the
numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past
propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. Find more good
information and tutorials on propagation at
http://myplace.frontier.com/~k9la/.

Monthly propagation charts between four USA regions and twelve
overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins.

Sunspot numbers for December 27 through January 2 were 78, 54, 49,
37, 87, 99, and 90, with a mean of 70.6. 10.7 cm flux was 106.8,
105.8, 104.3, 106.7, 113.6, 117.8, and 119, with a mean of 110.6.
Estimated planetary A indices were 1, 2, 3, 4, 2, 1, and 3, with a
mean of 2.3. Estimated mid-latitude A indices were 0, 2, 3, 4, 1, 1,
and 2, with a mean of 1.9.
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/EX