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Brrr … Cold winters in 17th century Europe, as shown in this painting by Hendrick Avercamp, may have been caused by a lack of solar activity after all.

BOSTON—For decades, astronomers and climatologists have debated whether a prolonged 17th century cold spell, best documented in Europe, could have been caused by erratic behavior of the sun. Now, an American solar physicist says he has new evidence to suggest that the sun was indeed the culprit.

The sun isn’t as constant as it appears. Instead, its surface is regularly beset by storms of swirling magnetic fields. As a result, like a teenager plagued with acne, the face of the sun often sprouts relatively dark and short-lived “sunspots,” which appear when strong magnetic fields inhibit the upwelling of hotter gas from below. The number of those spots waxes and wanes regularly in an 11-year cycle. However, even that cycle isn’t immutable.

In 1893, English astronomer Edward Maunder, studying historical records, noted that the cycle essentially stopped between 1645 and 1715. Instead, the sun was almost devoid of sunspots during this period. In 1976, American solar physicist John “Jack” Eddy suggested there might have been a causal link between this “Maunder Minimum” in the number of Sunspots and the contemporaneous Little Ice Age, when average temperatures in Europe were a degree centigrade lower than normal.

One might expect the absence of dark spots to make the sun slightly brighter and hotter. But the absence of other signs of magnetic activity, such as bright patches of very hot gas known as Faculae more than compensates for this effect. So in fact, the total energy output of the sun is lower during a solar minimum. If the minimum is prolonged, as it was in the second half of the 17th century, the dip in output might indeed affect Earth’s climate.


However, scientists have debated whether the effect could have been large enough. For instance, in a paper of the Geophysical Research Letters, solar physicist Karel Schrijver of the Lockheed Martin Advanced Technology Center in Palo Alto, California, and his colleagues argue that during the Maunder Minimum, the sun couldn’t have dimmed enough to explain the Little Ice Age. Even during a prolonged minimum, they claim, an extensive network of very small faculae on the sun’s hot surface remains to keep the energy output above a certain threshold level.

Not so, says Peter Foukal, an independent solar physicist with HelioPhysics Inc. in Nahant, Massachusetts, who contends that Schrijver and his colleagues are “assuming an answer” in a circular argument. According to Foukal, who presented his work at a  meeting of the American Astronomical Society, there is no reason to believe that the network of small faculae would persist during long periods of solar quiescence. In fact, he says, observations between 2007 and 2009, when the sun was spotless for an unusually long time, reveal that all forms of magnetic activity diminished, including the small-faculae network.

What’s more, detailed observations from orbiting solar telescopes have shown that the small faculae pump out more energy per unit surface area than the larger ones already known to disappear along with the sunspots. So if the small faculae start to fade, too, that would have an even stronger effect on the total energy production of the sun. “There’s tantalizing evidence that [during the Maunder Minimum] the sun may have actually dimmed more than we have thought until now,” Foukal says.

Even so, Foukal concedes that other factors, such as enhanced volcanic activity around the globe, may also have played a role in causing Europe’s Little Ice Age. Meanwhile, the biggest worry to solar physicists—and to society—is that no one knows what caused the sun’s prolonged quiescence in the first place. As far as anybody knows, a repeat of the Maunder Minimum could start within a few years with the next dip in the number of sunspots.

“Weakest Solar Cycle In Almost 200 Years”

The sun is acting bizarrely and scientists have no idea why. Solar activity is in gradual decline, a change from the norm which in the past triggered a 300-year-long mini ice age. We are supposed to be at a peak of activity, at solar maximum. The current situation, however, is outside the norm and the number of sunspots seems in steady decline. The sun was undergoing “bizarre behavior” said Dr Craig DeForest of the society. “It is the smallest solar maximum we have seen in 100 years,” said Dr David Hathaway of Nasa. –Dick Ahlstrom, The Irish Times, 12 July 2013

Illustration mapping the steady decline in sunspot activity over the last two solar cycles with predicted figures for the current cycle 24

The fall-off in sunspot activity still has the potential to affect our weather for the worse, Dr Elliott said. “It all points to perhaps another little ice age,” he said. “It seems likely we are going to enter a period of very low solar activity and could mean we are in for very cold winters.”

“We’re in a new age of solar physics,” says David Hathaway of NASA’s Marshall Space Flight Center in Huntsville, Alabama, who analysed the same data and came to the same conclusion. “We don’t know why the Gleissberg cycle takes place but understanding it is now a focus.” As for when the next Maunder minimum may happen, DeToma will not even hazard a guess. “We still do not know how or why the Maunder minimum started, so we cannot predict the next one.” –Stuart Clark, New Scientist, 12 July 2013


Solar Cycle 24 Weakest In Almost 200 Years – Shows Signs Of An Even Weaker Upcoming Cycle 25

The website of geologist Dr. Sebastian Lüning and Professor Fritz Vahrenholt, authors of the new book: “The Neglected Sun“, has a general solar activity progress report with some interesting observations on solar cycle 24 and comments about upcoming solar cycle 25

The Sun In July 2013 – News and Some Statistics
By Frank Bosse

According to the Solar Influences Data Analysis Center (SIDC) in Brussels, the “official” solar sunspot number (SSN) last month was 57.0. Thus it reached only 57% of the mean value of cycles 1-23 in the corresponding time period, see graph below: “Average Solar Cycle”:

The chart is a plot of sunspot number (SSN) versus months after the start of the cycle.dark blue: mean value of cycles 1-23, red curve is the current cycle 24, and the gray curve is cycle no. 5.

If you calculate using the entire Cycle 24. then we get an activity level that is only about 45% of the mean value. The comparison of all cycles up to the current month:

You have to go back all the way to 1827 (SC 7) to find a comparably small activity like what we have seen since 2009. Leif Svalgaard once called the sun a “messy place” in order to tell us that our mother star is always full of surprises. Could there be an unexpected increase in Solar Cycle 24 activity coming up and what is the probability of that happening? Here the solar sunspot number anomalies of the previous chart (ASSA 56 – the accumulated solar sunspot anomaly after 56 months after the start of the cycle) is compared to the total sum of the anomalies (ASSA acc) of the previous cycles 1-23:

Result: There’s a very high probability (average 88%) that we will continue to see an extremely weak solar cycle. A lot indicates an anomaly of -2400 at the end of Cycle 24. Signs show that we are already past the maximum. Also renowned the website spaceweather.com determined this on 26 July 2013. Readers of our monthly Sonneninfo already suspected this earlier (see “The sun in June 2013 – on the way to a grand minimum? New work on the possible consequences“). Here the polar solar fields were depicted. Last month also confirmed the measurement data: The polarity has switched and the maximum is behind us. So how long will the weakening of SC24 take?

This question is hardly unimportant for telling us what to expect from the upcoming SC25. It has long been known that a long solar cycle of weaker activity is followed by a similar cycle, and vice versa. When you plot the length of the previous cycle with accumulated sunspot anomaly (“ASSA acc”) together with the following cycle, you get this interesting diagram:

Blue curve shows SCn (months) *(-1); Red curve ASSA (SCn+1)

The inverted cycle length of Cycle 1 (blue) was compared with the ASSA acc (red) of the subsequent Cycle 2. Just the length of Cycle 23 (May 1996 until November 2008: 150 months instead of 131.5=10.9 years on average) should have led to the prediction of a weaker Cycle 24, the correlation is over 0.7. In the meantime David Hathaway of NASA has recognized: “Relationships have been found between the size of the next cycle maximum and the length of the previous cycle…”.

Summarizing: The current Cycle 24 is in total the weakest since 1820, the probability of a change into stronger activity is only 12% and the length of the cycle can certainly be a useable indicator for the development of the upcoming cycle 25. If solar scientists Livingtson and Penn are correct, SC 25 may be even weaker than SC 24  should the magnetic field strength B in the lower chart fall to 1400 Gauss on average. Below this limit no sunspot can be created, as you can see at the bottom of the chart. The last time that happened, it is suspected, was during the solar Maunder Minimum from 1645-1715.

Source: leif.org