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Past and future
of deep time Solar Cycles
The some what orderly
solar cycles that have been observed for a little over three hundred years
or so have ebbed and flowed producing some very intense solar maximum
(Peak sunspot and solar activity) and sometimes almost not shown at all.
The low intensity solar cycles, particularly when there has been a
succession of them appear to have a connection with general climatic
conditions on Earth. Periods
such as the Maunder
Minimum from about 1650 to 1715 saw very few reports of sunspots
and coincided with the coldest part of the period known as the Little Ice
Age.
The absence of sunspots
or a very active Sun in terms of sunspot activity seems to have very
little observable change in total solar output; therefore a connection
between sunspot activity and the Earth’s climate has struggled to gain
credibility. The mechanism may not be entirely understood, but historic
records of climate and sunspot activity seems to indicate a connection.
The sunspot connection
may at the very lest be a contributing factor as it may have been during the
relatively recent Dalton Minimum. The Dalton
Minimum was a period of low solar activity, lasting from about 1790
to 1820 that also coincided with a period of lower than average global
temperatures.
The cooler temperatures
were exasperated by the eruption in 1815 of
Mount
Tambora
on the
island
of
Sumbawa
, in what is now
Indonesia
. This made the winter of 1816
one of the most miserable and deadly on recorded. The volcanic eruption clearly made things worse, but the cold spell was
well underway from about 1810.
A determination of solar
activity for the last 11,000 years has been made using the carbon 14 proxy
record.
The Earth is constantly
being irradiated by cosmic rays from deep space and these rays produce in
the atmosphere a material known as carbon 14 which is absorbed by trees
among other things. Trees even dead trees retain a record of the levels of
carbon 14 being produced over a very long period of time. Charged
particles from the Sun which are greater during periods of high sunspot
activity repel the cosmic rays and therefore the more sunspot activity
there is the less carbon 14 is recorded in the tree rings.
Using the carbon 14 level
records the sunspot number estimates have been pushed back as far as
11,400 years into the past.
This determined record of
solar activity sees a striking correlation between low solar activity and
a series of well document cool climate periods during this time.
Seeing
order in the chaos
These seemingly random
periods of low sunspot activity may have more order and predictability
than appears at first glance.
An interesting paper
written by I.
Charvâtova in 1999 regarding Celestial
Barycentrics (The orbital mechanics of the solar system) speculates
about much longer duration cycles that impact on the behaviour of the sun
and by extension the earth’s climatic conditions.
Not generally appreciated
is the fact the planets of the solar system do not actually orbit around
the sun, they including the sun orbit around the centre of the solar
system’s total mass. The Sun representing 99.8% of the total solar
system’s mass orbits around a point very close to the centre, however it
can be more than a Sun diameters from the central point.
The mechanics of objects
orbiting around the central point of the mass in a celestial system can be
more clearly seen when the orbits of binary stars are observed. Take a two
star system where both stars are identical in mass, both stars will orbit
around a point half way between each other.
Our sun is influenced by
the distribution of the total solar system’s mass, but primarily by the
positions of the four largest planets in order of mass, Jupiter, Saturn,
Uranus and Neptune. The below plot the Sun’s position in relation to
solar systems centre point over a fifty year period from 1945 to 1995
clearly shows the dynamics of this tug of war between the system heavy
weights. See Fig. 1.
It is in fact by
observing the wobble of distant stars that astronomer are able to
determine if that star has planets, the size of the planets and the orbit
of the planets about the star. This technique is the method that has
resulted in the discovery of all the so called exoplanets (Planets outside of our solar system) to date.
Fig.
1:
The sun's diameter is marked by a thick circle. The position of the centre
of mass relative to the sun's centre marked by a cross and the respective
years is indicated by small circles.
The orbit of our Sun
around the central and moving centre mass of the solar system generally
forms a well ordered pattern referred to as a Trefoil. See below the
pattern that is referred to as a Trefoil pattern.
Fig.
2: Trefoil pattern sometimes
referred to as the trefoil
knot.
The
Trefoil pattern or something resembling it is the norm and appears
associated with long periods of relatively consistent solar cycles,
however every now and then this pattern is disrupted and a period of disordered
motion grips the Sun. This abnormal disordered period appears to be
associated with less sunspot activity and generally lower temperatures
here on Earth.
The
study by the author proposes that the 4 most influential planets orbiting
around the our Sun produce a number of repeating cycles, a 2402 year
cycle, a number of 178 year periods within the 2402 years, and a 370 year
period also within the 2402 year cycle. They also reveal the order
and chaos within the motions of the Sun around the centre of mass within
these periods.
The
below diagram show the Sun’s path around the centre of mass of the solar
system for defined periods of time starting in the year 1192 to the year
2134. The six upper plots show the Sun’s path in the orderly Trefoil
type pattern. The lower five plots show the disordered path and the
related grand
minima that also saw temperature plunge on Earth.
Fig.
3: Diagram
of the Sun’s path around the centre of mass of the solar system for
defined periods of time starting in the year 1192 to the year 2134.
Of
interest to us right now is that we are entering (since 1985 and on going
too until 2040) one of these periods of "disordered" motion.
What is most interesting is that the last four "disordered"
periods coincided with the "Wolf", "Sporer",
"Maunder", and "
Dalton
" climate minimums.
The
table below clearly shows that while the grand minimums are not all that
common they can however last some time.
|
Duration
centre year
|
Duration
in years
|
Name
|
|
1810
|
40
|
Dalton
|
|
1680
|
80
|
Maunder
|
|
1470
|
160
|
Spörer
|
|
1305
|
70
|
Wolf
|
What’s
this have to do with radio?
The
solar cycles clearly have everything to do with radio propagation as it is
typically experienced on the HF and low VHF bands. However such long
duration cycles that are at a minimum several generations in length are
difficult to apply practically to ham radio operations. It is more a point
of interest in the ongoing speculation of what the next cycle will bring
and how this marvellous natural feature may in fact work! It is of
particular interest with respect of the new cycle 24 and how it might
develop with the view that we are well into a period of disordered motion
as proposed in the author’s paper. We may have front row seats into a
greater understanding of not only the solar cycles, but also to the
effects on the Earth’s climatic conditions by the subtle
affects of these solar cycles.
A
grand minimum would make the depressed HF conditions that we have been
experiencing for 2008 the norm for the next generation or three.
All
this may be a bit depressing if you like me were looking forward to nice
big solar max, but maybe we have more to worry about other than not seeing
that fantastic F2 opening to Hawaii on six metre! If the past is any guide
a grand minimum would likely disrupt food production, promote famines and
for those living in the extreme northern and southern latitudes could be
directly life threatening.
The
arguments proposed in Charvâtova’s paper are far from holding centre
stage, however the test of time and observation will determine its place
in our understanding of the relationship that the Earth and her occupants
have with the greater universe.
For
more information on long term solar cycles.
See:
http://www.ann-geophys.net/18/399/2000/angeo-18-399-2000.pdf
Author:
I.
Charvâtova
Geophysical
Institute
AS
CR, Bočnĭ II, 141 31 Praha 4,
Czech
Republic
Received:
30 September 1999 / Revised: 14 January 2000 / Accepted: 17 January 2000
For
more information on centre of mass dynamics. See:
http://astro.unl.edu/naap/esp/centerofmass.html
For
more information on Extrasolar planets. See:
http://en.wikipedia.org/wiki/Extrasolar_planet
For
more information on the effects of grand minimums on climate. See:
http://en.wikipedia.org/wiki/Little_Ice_Age
Also see earlier article
‘The Restless Sun - Past and Future of the Solar Cycle’
(Published in the
WANSAC magazine Vol 38 Issue September and October 200)
http://vk6ysf.com/solarcycles1.htm
Cheers,
Happy DXing and keep warm!
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