Monday, March 22, 2010

The Continuing Decline of the Sun — New Data

The Frozen Thames, London, 1677
click for larger image

Despite the recent increase in solar activity, the sun is still behaving very strangely.

In 2006, Dr. William Livingston and Dr. Matthew Penn, of the National Solar Observatory in Tucson, wrote a paper describing their observations showing that the relative darkness and magnetic field strength of sunspots have been declining independently of the normal sunspot cycle since 1990. They predicted that if this continues, sunspots would disappear entirely from the sun sometime between 2015 and 2020. It is not clear when they would return.

The paper was never accepted for publication, primarily because no one had a theory to account for the observations. Since that time, measurements have continued to show an almost linear decline in both spot darkness and magnetic field.

The Hunters in the Snow by Pieter Brueghel the Elder, 1565
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It has been hypothesized that this dimming is similar to what happened during the Maunder Minimum that lasted from 1645 to 1715. It coincided with the Little Ice Age, a time of extraordinarily cold winters and crop failures throughout the world. While there is a dispute among scientists whether or not the Maunder Minimum actually "caused" the Little Ice Age, many believe that solar magnetic/plasma activity, measured by the quantity and size of sunspots, affects climate through a number of mechanisms, including such obscure things as the modulation of the cosmic ray flux reaching the earth, which may cause changes in cloud formation.

If a Little Ice Age were to occur today, with our present world population, we could see famine, war, and economic collapse worldwide.

The Livingston and Penn Data
click for larger image

On Friday, I asked for and received Livingston and Penn's raw data, including the most recent observations, from another solar physicist. My plot shown above is similar to the chart available in this thread, but provides a little more resolution and detail. I also plotted the yearly averages as large dots, centered on the middle of each year. The dot for 2010 represents just the data so far recorded.  It should be mentioned that the data in the 1990's is sparse and is therefore less certain.

The "umbral intensity ratio" is a measurement of the continuum intensity of the dark part of the sunspot (umbra) as a ratio to the surrounding quiet sun.  When this ratio is equal to 1, the sunspot is invisible (or doesn't exist).  The sunspot magnetic field is measured by the Zeeman splitting of the iron (Fe) spectral lines.    When the magnetic field is less than 1500 gauss, the sunspot does not form.  L&P have also measured an absolute temperature change using a molecular technique, but that data is not shown here.

As you can see, the data varies quite a bit, but the noise is in the real solar phenomena, not in the measurement technique.  Regardless, there are clear trends as indicated by second order polynomial fits to the data.  The umbral intensity ratio is increasing toward 1, and the magnetic field is decreasing.  The fit is almost linear.

Livingston and Penn get telescope time infrequently, and measurements are often impossible due to weather conditions.  Also, the unusually deep 11-year solar cycle minimum for the last three years has afforded few spots to measure.  So sometimes, months go by with no observations at all.

It is very important to note that this solar decline has been unaffected by the peaks and valleys of the 11-year solar cycle, and appears to be a completely independent phenomenon.  The fact that it is continuing during the higher activity now being seen as solar cycle 24 ramps up is further confirmation of its independent nature.

The L&P dimming of sunspots is independent of this data showing the ramp up in solar activity in recent months.  Shown are Total Solar Intensity, the 10.7 meter radio flux, the overall solar magnetic field, and the number of sunspots (

If this behavior continues, I believe that we may be in quite a bit of trouble.  Even a shorter and shallower minimum such as the Dalton Minimum in the early 1800s would be bad.  A degree or two of extra warmth is much preferred to killing freezes.

 Winter skating on the main canal of Pompenburg, Rotterdam in 1825,
by Bartholomeus Johannes van Hove


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