Solar Science

I’m not going to add much more than to say that its enjoyable and refreshing to see a senior scientist admit that they were wholly wrong in their predictions.

How Long Will Our Sun Remain Quiet and Cosmic Rays Increase?

What Happened to 2006 Predictions of Huge Solar Cycle 24?

ISN’T IT ESPECIALLY STRANGE FOR YOU BECAUSE THREE YEARS AGO, ALL THE PHYSICS OF THE SUN THAT YOU AND NASA AND EVERYBODY ELSE WAS USING WERE ANTICIPATING THAT THIS COULD BE THE BIGGEST SOLAR MAXIMUM ON RECORD?

There were indications back then. I am writing a paper – it’s on my computer as we speak (laughs) – basically saying that I made a big mistake – myself and Bob Wilson – when we wrote a paper in 2006, suggesting Solar Cycle 24 was going to be a huge cycle based on conditions at that time. The problem we had with our prediction was that it was based on a method that assumes that we’re near sunspot cycle minimum.

We had just previously gone through three or four sunspot cycles that had been only ten years long each, so for the one in 1996 to 2006, it seemed like a reasonable assumption. But as we now know, we were off by at least two years. And if we take conditions on the sun now, it’s a completely different story. The conditions now – using even that same technique from 2006 – says that the next sunspot cycle is going to be half what we thought it was back in 2006.

Another big prediction in 2006 was based on a dynamo model – a model for how the sun produces magnetic fields – and it suggested a huge cycle.

But there also were people back at that time saying otherwise. A group of colleagues led by Leif Svalgaard, Ph.D., were looking at the sun’s polar fields and saying even at that point, the sun’s polar fields were significantly weaker than they had been before and those scientists back then predicted it was going to be a small cycle.

How Small Will Solar Cycle 24 Be?

…I’ve come around to that view now. I think there is little doubt in my mind now that we’re in for a small cycle. The big question now is how small? I think most of us are predicting small cycles. I think even the techniques I’m using now are suggesting HALF the size of the last three or four solar cycles, but my fear is that even that might be too big just from the fact that it’s taken so long for this Solar Cycle 24 to really get off the ground and start producing sunspots.

I have no doubt at this point that it’s going to be a little cycle. My current prediction is that it’s going to be about half of what we’ve seen in the last four solar cycles or so. But in my gut, I feel it’s going to be smaller than that! (laughs) It’s just so slow in taking off and the indicators that we see – both the polar fields and the geomagnetic indicators are lower than anything we’ve seen before.

So kudos to David Hathaway for writing a paper talking about how wrong his previous papers have been. Absolutely no sarcasm intended or implied.

This just in from NASA:

September 3, 2009: The sun is in the pits of the deepest solar minimum in nearly a century. Weeks and sometimes whole months go by without even a single tiny sunspot. The quiet has dragged out for more than two years, prompting some observers to wonder, are sunspots disappearing?

“Personally, I’m betting that sunspots are coming back,” says researcher Matt Penn of the National Solar Observatory (NSO) in Tucson, Arizona. But, he allows, “there is some evidence that they won’t.”

Penn’s colleague Bill Livingston of the NSO has been measuring the magnetic fields of sunspots for the past 17 years, and he has found a remarkable trend. Sunspot magnetism is on the decline:

Above: Sunspot magnetic fields measured by Livingston and Penn from 1992 – Feb. 2009 using an infrared Zeeman splitting technique.

“Sunspot magnetic fields are dropping by about 50 gauss per year,” says Penn. “If we extrapolate this trend into the future, sunspots could completely vanish around the year 2015.”

Hmmm, yes they could. But the solar magnetic field could simply be in a cyclical downturn of which this is a part. We need an expert!

“This work has caused a sensation in the field of solar physics,” comments NASA sunspot expert David Hathaway, who is not directly involved in the research. “It’s controversial stuff.”

The controversy is not about the data. “We know Livingston and Penn are excellent observers,” says Hathaway. “The trend that they have discovered appears to be real.” The part colleagues have trouble believing is the extrapolation. Hathaway notes that most of their data were taken after the maximum of Solar Cycle 23 (2000-2002) when sunspot activity naturally began to decline. “The drop in magnetic fields could be a normal aspect of the solar cycle and not a sign that sunspots are permanently vanishing.”

Yes, what he said.

Penn himself wonders about these points. “Our technique is relatively new and the data stretches back in time only 17 years. We could be observing a temporary downturn that will reverse itself.”

The technique they’re using was pioneered by Livingston at the NASA-supported McMath-Pierce solar telescope near Tucson. He looks at a spectral line emitted by iron atoms in the sun’s atmosphere. Sunspot magnetic fields cause the line to split in two—an effect called “Zeeman splitting” after Dutch physicist Pieter Zeeman who discovered the phenomenon in the 19th century. The size of the split reveals the intensity of the magnetism

If the solar magnetism continues to decline what could this mean for the Earth?

If sunspots do go away, it wouldn’t be the first time. In the 17th century, the sun plunged into a 70-year period of spotlessness known as the Maunder Minimum that still baffles scientists. The sunspot drought began in 1645 and lasted until 1715; during that time, some of the best astronomers in history (e.g., Cassini) monitored the sun and failed to count more than a few dozen sunspots per year, compared to the usual thousands.

Note that of course, they don’t mention that this coincided with the coldest part of the Little Ice Age. But that would be politically incorrect, wouldn’t it?

“Whether [the current downturn] is an omen of long-term sunspot decline, analogous to the Maunder Minimum, remains to be seen,” Livingston and Penn caution in a recent issue of EOS. “Other indications of solar activity suggest that sunspots must return in earnest within the next year.”

I’d love to know what those other indications are, because the prognostications of future solar activity have been startlingly poor from practically everybody.

I leave the last words to David Hathaway, who dares to speak the truth to solar science:

Whatever happens, notes Hathaway, “the sun is behaving in an interesting way and I believe we’re about to learn something new.”

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Previously on this blog, I’d mentioned my skepticism that one decent sunspot marked the end of the hiatus in the solar cycle we’ve seen for nearly two years. It might be my nature, but everybody has been wrong before.

As part of my public duty to actually ask real scientists monitoring the Sun, I wrote to Dr Ken Tapping of Canada’s National Research Council at the Herzberg Institute of Astrophysics in British Columbia:

Dear Dr Tapping

For the first time in a very long time, the Sun has managed to produce a sunspot (1024) which has lasted more than a few hours.

Is there any sign of an upswing in radio emissions indicating an end to the hiatus?

Best regards

John

and Dr Tapping replied (with my emphasis):

Hi John,

Last weekend I saw a really nice sunspot group on the Sun, which could have been part of the new cycle. The solar radio flux went up a little while it was there. However now the flux has slumped back to low values again.

Some theorists have suggested the new cycle is currently under way, but that for some unknown reason we are not getting the spots to go with it. I’m not sure what that really means, so I am making no suggestion as to what is going on.

Being very conservative, according to the measurements being made under our Solar Radio Monitoring Programme, we have yet to see signs the next cycle is really under way.

Regards,

Ken

Now this is what I’d thought, that the nice sunspot (1024) we’d seen did not presage a change in the behavior of the Sun: the solar wind speed remained subdued, coronal holes remained very small, there were no prominences to speak of.

It also baffles me how “some theorists have suggested the new cycle is currently under way, but that for some unknown reason we are not getting the spots to go with it”. If there are very few sunspots and the radio flux remains extremely subdued, on what basis are these theorists making their statements?

It could be that this is the first “radio quiet” solar cycle … anyone believe that?

So for solar physicists, it remains “interesting times” and probably a time to clear out some old theories and start again.

My thanks to Dr Tapping for the correspondence.

I’ve noticed that David Hathaway is not backing down from his previous predictions that SC24 will be a) larger than SC23 and b) the length of SC24 will be approximately the same as previous cycles.

Here is the update:

Predicting the behavior of a sunspot cycle is fairly reliable once the cycle is well underway (about 3 years after the minimum in sunspot number occurs [see Hathaway, Wilson, and Reichmann Solar Physics; 151, 177 (1994)]). Prior to that time the predictions are less reliable but nonetheless equally as important. Planning for satellite orbits and space missions often require knowledge of solar activity levels years in advance.

A number of techniques are used to predict the amplitude of a cycle during the time near and before sunspot minimum. Relationships have been found between the size of the next cycle maximum and the length of the previous cycle, the level of activity at sunspot minimum, and the size of the previous cycle.

Among the most reliable techniques are those that use the measurements of changes in the Earth’s magnetic field at, and before, sunspot minimum. These changes in the Earth’s magnetic field are known to be caused by solar storms but the precise connections between them and future solar activity levels is still uncertain.

Of these “geomagnetic precursor” techniques three stand out. The earliest is from Ohl and Ohl [Solar-Terrestrial Predictions Proceedings, Vol. II. 258 (1979)] They found that the value of the geomagnetic a index at its minimum was related to the sunspot number during the ensuing maximum. The primary disadvantage of this technique is that the minimum in the geomagnetic aa index often occurs slightly after sunspot minimum so the prediction isn’t available until the sunspot cycle has started.

An alternative method is due to Joan Feynman. She separates the geomagnetic aa index into two components: one in phase with and proportional to the sunspot number, the other component is then the remaining signal. She found that this remaining signal faithfully represents the sunspot numbers several years in advance. The maximum in this signal occurs at sunspot minimum and is proportional to the sunspot number during the following maximum. This method does allow for a prediction of the next sunspot maximum at the time of sunspot minimum.

A third method is due to Richard Thompson [Solar Physics 148, 383 (1993)]. He found a relationship between the number of days during a sunspot cycle in which the geomagnetic field was “disturbed” and the amplitude of the next sunspot maximum. His method has the advantage of giving a prediction for the size of the next sunspot maximum well before sunspot minimum.

We have employed these methods along with several others to determine the size of the next sunspot cycle using a technique that weights the different predictions by their reliability. [See Hathaway, Wilson, and Reichmann J. Geophys. Res. 104, 22,375 (1999)] This analysis indicated (by mid-1996) a maximum sunspot number of about 154 ± 21. We then use the shape of the sunspot cycle as described by Hathaway, Wilson, and Reichmann [Solar Physics 151, 177 (1994)] and determine a starting time for the cycle by fitting the data to produce a prediction of the monthly sunspot numbers through the next cycle. We find a starting time of July 1996 with minimum occuring in October 1996. The predicted numbers are available in a text file, as a GIF image, and as a Postscript file. As the cycle progresses, the prediction process switches over to giving more weight to the fitting of the monthly values to the cycle shape function. At this phase of cycle 23 we now give full weight to the curve-fitting technique of Hathaway, Wilson, and Reichmann Solar Physics 151, 177 (1994). The two parameters for this fit (cycle amplitude and cycle starting time) have remained unchanged since early 1999.

Note: These predictions are for “smoothed” International Sunspot Numbers. The smoothing is usually over time periods of about a year or more so both the daily and the monthly values for the International Sunspot Number should fluctuate about our predicted numbers. Also note that the “Boulder” numbers reported daily at www.spaceweather.com are typically about 35% higher than the International sunspot number.

Another indicator of the level of solar activity is the flux of radio emission from the Sun at a wavelength of 10.7 cm (2.8 GHz frequency). This flux has been measured daily since 1947. It is an important indicator of solar activity because it tends to follow the changes in the solar ultraviolet that influence the Earth’s upper atmosphere and ionosphere. Many models of the upper atmosphere use the 10.7 cm flux (F10.7) as input to determine atmospheric densities and satellite drag. F10.7 has been shown to follow the sunspot number quite closely and similar prediction techniques can be used. Our predictions for F10.7 are available in a text file, as a GIF image, and as a Postscript file. Current values for F10.7 can be found at:
http://www.drao.nrc.ca/icarus/www/sol_home.shtml

Now the reason why I quote the entire blog post in full is because, for some reason, Dr Hathaway won’t blog in sequential format the way normal people do, instead preferring to re-edit his previous posts.

Editing history is Orwellian, Dr Hathaway

I thought I’d give a little heads up to a conference to be held at Montana State University from June 1-6:

Approximately 100 scientists from Europe, Asia, Latin America, Africa and North America will participate in the workshop titled “Solar Variability, Earth’s Climate and the Space Environment,” said MSU physicist Dibyendu Nandi, head of the local organizing committee.

Participants will include directors of major international institutions, leaders of space missions and contributors to the report of the Intergovernmental Panel on Climate Change. One of the participants, the managing director of the Max-Planck-Institute for Solar System Research in Germany, will give a public address on June 3.

“This is the first workshop in this international series of meetings that will be held in the United States,” said William Hiscock, physics professor and head of the MSU physics department. “The selection of MSU as host for this event reflects the strong international reputation of our solar physics research group.”

Nandi added, “The Sun is the main source of energy in the solar system. Understanding how variations in its magnetic and radiative output influence our climate and space environment is the primary focus of this workshop. Achieving this understanding is important for protecting our technologies in space and on Earth and is essential towards distinguishing the natural and man-made causes of global climate change.”

Of course, some climate modellers think that this conference would be a waste of time.

I look on solarcycle24.com. I see a high latitude sunspot number 992.

I think “hurrah! SC24 has finally shown itself”. I check the magnetogram.

The black arrow points to sunspot 992 – and its an SC23 spot! Its the same polarity as the SC23 magnetic signatures further south.

The red arrow points to the reversed polarity SC24 phage left by the tiny SC24 spot left a week ago.

Fool me.

Much excitement from NASA, as the long delayed arrival of Solar Cycle 24 was announced:

Dec. 14, 2007: The solar physics community is abuzz this week. No, there haven’t been any great eruptions or solar storms. The source of the excitement is a modest knot of magnetism that popped over the sun’s eastern limb on Dec. 11th, pictured below in a pair of images from the orbiting Solar and Heliospheric Observatory (SOHO).

It may not look like much, but “this patch of magnetism could be a sign of the next solar cycle,” says solar physicist David Hathaway of the Marshall Space Flight Center.

Yeees, go on…

“New solar cycles always begin with a high-latitude, reversed polarity sunspot,” explains Hathaway. “Reversed polarity ” means a sunspot with opposite magnetic polarity compared to sunspots from the previous solar cycle. “High-latitude” refers to the sun’s grid of latitude and longitude. Old cycle spots congregate near the sun’s equator. New cycle spots appear higher, around 25 or 30 degrees latitude.

OK, got that. Now we have a sunspot with reversed polarity compared to solar cycle 23?

The region that appeared on Dec. 11th fits both these criteria. It is high latitude (24 degrees N) and magnetically reversed. Just one problem: There is no sunspot. So far the region is just a bright knot of magnetic fields. If, however, these fields coalesce into a dark sunspot, scientists are ready to announce that Solar Cycle 24 has officially begun.

And did this coalesce into a sunspot? No. The Sun remains stubbornly blank although there was a fair sized SC23 spot for several days that followed.There appears to be indications of a large sunspot on the far side of the Sun but that too is right on the equator and probably isn’t polarity reversed from SC23.

This isn’t the first time that a sunspot appeared to herald the next solar cycle that failed to materialize. There was another which appeared in late 2006 that got people excited for literally hours when it appeared and disappeared.

Hathaway, it must be remembered, was one of a team who predicted a very strong SC24, at least as strong as the previous one. I think the tension may be getting to him.

I think its OK to actually wait for at least a couple of magnetically reversed sunspots to appear at high latitudes before announcing the Coming of the next Solar Cycle. Whatever happens, SC24 will be late.

From NASA website:

Solar cycle 24, due to peak in 2010 or 2011 “looks like its going to be one of the most intense cycles since record-keeping began almost 400 years ago,” says solar physicist David Hathaway of the Marshall Space Flight Center. He and colleague Robert Wilson presented this conclusion last week at the American Geophysical Union meeting in San Francisco.

Their forecast is based on historical records of geomagnetic storms.

Hathaway explains: “When a gust of solar wind hits Earth’s magnetic field, the impact causes the magnetic field to shake. If it shakes hard enough, we call it a geomagnetic storm.” In the extreme, these storms cause power outages and make compass needles swing in the wrong direction. Auroras are a beautiful side-effect.

Hathaway and Wilson looked at records of geomagnetic activity stretching back almost 150 years and noticed something useful:. “The amount of geomagnetic activity now tells us what the solar cycle is going to be like 6 to 8 years in the future,” says Hathaway. A picture is worth a thousand words:

Hathaway's comparison of solar and geomagnetic fields

Above: Peaks in geomagnetic activity (red) foretell solar maxima (black) more than six years in advance. [More]

In the plot, above, black curves are solar cycles; the amplitude is the sunspot number. Red curves are geomagnetic indices, specifically the Inter-hour Variability Index or IHV. “These indices are derived from magnetometer data recorded at two points on opposite sides of Earth: one in England and another in Australia. IHV data have been taken every day since 1868,” says Hathaway.

Cross correlating sunspot number vs. IHV, they found that the IHV predicts the amplitude of the solar cycle 6-plus years in advance with a 94% correlation coefficient.

“We don’t know why this works,” says Hathaway. The underlying physics is a mystery. “But it does work.”

And here’s the prediction for Solar Cycle 24 based on this “mystery”:

Hathaway's 2006 prediction of SC24

Never mind that this thing looks a lot like numerology – if its from NASA and has a nice graph it must be worth something

This blog was setup by me to collate news on solar physics, predictions of future solar activity and possible correlations between solar activity and the Earth’s climate of the past.

I don’t come to any firm conclusions about the effect of solar variation on the climate of the Earth. I am merely reporting what I see.