ARRL

ARRL Propagation Bulletin ARLP029 (2011)

SB PROP @ ARL $ARLP029
ARLP029 Propagation de K7RA

ZCZC AP29
QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 22, 2011
To all radio amateurs 

SB PROP ARL ARLP029
ARLP029 Propagation de K7RA

Average daily sunspot numbers for the week rose nearly 27 points to
92.4, while average daily solar flux increased over 9 points to
98.2.  The latest prediction has solar flux values for the next week
a little lower than those listed in Thursday's ARRL Letter.
Expected values are 96 for today, July 22, then 95 on July 23-27, 98
on July 28, 90 on July 29 through August 2, 95 on August 3-7, 98 on
August 8, and back to 100 on August 9-16.
 
Planetary A index for July 22-23 is predicted at 10 and 8, then 5 on
July 24-28, 8 on July 29-31, then 10, 8, 5 and 8 on August 1-4, 12
on August 5-7, and 8 on August 8-10.
 
Geophysical Institute Prague has a weekly prediction for geomagnetic
indices that doesn't use the A or K index, but instead has seven
levels of activity, from quiet to severe storm.  Their prediction
for this week says to expect unsettled conditions for today, July
22, quiet to unsettled on July 23, quiet July 24-25, quiet to
unsettled July 26-27, and quiet again on July 28.
 
There seem to be plenty of sunspots visible over the past week, but
nothing really large or very active.  Sunspot areas are counted in
millionths of a solar hemisphere, and on Thursday, July 14, there
were six sunspot groups visible:  1245, 1250, 1251, 1252, 1254 and
1255.  The area ranged from 5 for sunspot group 1245 to 100 each for
groups 1250 and 1251.  Total sunspot area for that day was 265.
 
On Friday, July 15, a new sunspot group 1256 was added, and total
sunspot area was 260, as the other sunspot groups shrank, except for
1251 and 1254.  On July 16, 1255 disappeared, and total sunspot area
dropped to 230.  On Sunday, July 17, sunspot areas 1245 and 1252
disappeared, new group 1257 was added, and total sunspot area grew
to 280.
 
On Monday, July 18 sunspot area jumped to 400 when two new groups,
1258 and 1259 were added.  On July 19 sunspot area jumped again to
660, when 1255 disappeared and all sunspot groups except 1256 grew.
1250, 1257 and 1258 each doubled in size, while 1259 more than
tripled.
 
On July 20, 1256 and 1257 disappeared, and sunspot area dropped by
more than half to 310.  Yesterday, July 21, 1250 and 1258 went away,
and sunspot area declined from 310 to 290, and daily sunspot number
declined from 79 to 56.
 
There has been quite a bit of news about a predicted grand minima in
solar activity.  We recently reported on a conference in which three
lines of evidence were presented which seemed to point to a future
disappearance of sunspots, perhaps like the dreaded Maunder Minimum.
 
I am not unbiased in this regard, and like most amateur radio
operators yearn for high solar activity.  Alas, a return of cycle
19, the granddaddy of them all, seems elusive.  But there is some
dissent regarding these predictions of no sunspots, which gives us
hope.
 
On Wednesday I spoke with Dr. Douglas Biesecker, an astrophysicist
at the NOAA Space Environment Center in Boulder.  He was mentioned
in ARLP024 (see http://www.arrl.org/w1aw-bulletins-archive/ARLP024/2011) 
as dissenting from the assertion that evidence points toward sunspots 
disappearing or another Maunder Minimum in our future.
 
He mentioned something called a Gleissberg Cycle.  What happens when
we do a really long smoothing of sunspot numbers?  The smoothed
sunspot numbers we are familiar with, the data used in those nice
graphs of sunspot cycles, average data over 13 months.  So every
place you look on the graph doesn't show the variation that occurred
during that month, but instead averages data over more than a year,
to smooth out all the noise of daily variations.
 
But what would happen if you smoothed the numbers over a much longer
period, say 11 years?  Could you find some periodicity that would
suggest a cycle of cycles, or perhaps predict clusters of decades
with low or high solar activity?
 
Gleissberg cycles suggest a periodicity of about 87 years, and some
have studied these to try to predict general levels of solar
activity over multiple decades.  But if a cycle is 87 years long,
and we only have about 256 years of directly observed solar data,
the most we could look at would be less than three cycles.  That
isn't enough data to make even crude speculative projections.
 
Doug mentioned what he referred to as an "old NASA axiom", that goes
something like this:  If you can't see something happen seven times,
it isn't real.
 
Doug said he is attending SHINE workshops, and SHINE is an acronym
for Solar Heliospheric and Interplanetary Environment (see
http://shinecon.org/).  At these meetings participants have been
hashing out the evidence for or against a "no cycle 25" scenario,
and discovering some problems with the three lines of evidence
pointing toward a disappearance of sunspots.  They haven't reached a
consensus, but he believes that positions may be moving away from
predicting another Maunder Minimum.
 
On this topic, take a look at this website:
http://www.thesuntoday.org/current-observations/solar-hibernation-much-ado-about-nothing/.
 
A new issue of WorldRadio is available on the twentieth of each
month, and on July 20 the August 2011 issue was out.  You can get
one at http://www.worldradiomagazine.com/ and on page 20 you'll find
the monthly Propagation column by Carl Luetzelschwab, K9LA.  This
time it is titled "Here's Some Help to Explain Those Unusual QSOs".
Carl looks at propagation that doesn't seem to be supported by the
MUF or general level of solar activity at the time, and offers some
interesting ideas on what might really be going on.
 
If you are fortunate enough to be in Kansas City this weekend, you
can catch Carl's talk on propagation at W0DXCC-2011 on Saturday,
July 23.  His talk begins at 9:30 AM in the W0JM Room, and is titled
"Our Recent Sunspot Minimum, and the new Sunspot Cycle 24".  Check
http://www.w0dxcc.com/ for details.
  
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://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://mysite.ncnetwork.net/k9la/index.html.
 
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 July 14 through 20 were 79, 90, 75, 101, 127,
96, and 79, with a mean of 92.4.  10.7 cm flux was 94.1, 93.8, 93.8,
103.6, 102, 100.3, and 100.1, with a mean of 98.2.  Estimated
planetary A indices were 8, 6, 6, 5, 8, 18, and 19, with a mean of
10. Estimated mid- latitude A indices were 6, 5, 4, 3, 6, 10, and
12, with a mean of 6.6.
NNNN
/EX