I initially wrote this article using data only from David Archibald, but within a couple of minutes I was given some broader data from Leif Svalgaard, so I have rewritten this to include both resources in the interest of seeing the broader perspective. – Anthony
Last September WUWT covered NASA’s press conference on the state of the sun. One of the announcements was this:
Sept. 23, 2008: In a briefing today at NASA headquarters, solar physicists announced that the solar wind is losing power.
“The average pressure of the solar wind has dropped more than 20% since the mid-1990s,” says Dave McComas of the Southwest Research Institute in San Antonio, Texas. “This is the weakest it’s been since we began monitoring solar wind almost 50 years ago.”
From Wiki:
The solar wind is a stream of charged particles—a plasma—ejected from the upper atmosphere of the sun. It consists mostly of electrons and protons with energies of about 1 keV. The stream of particles varies in temperature and speed with the passage of time. These particles are able to escape the sun’s gravity, in part because of the high temperature of the corona, but also because of high kinetic energy that particles gain through a process that is not well-understood.
The solar wind creates the Heliosphere, a vast bubble in the interstellar medium surrounding the solar system. Other phenomena include geomagnetic storms that can knock out power grids on Earth, the aurorae such as the Northern Lights, and the plasma tails of comets that always point away from the sun.The solar wind is a stream of charged particles—a plasma—ejected from the upper atmosphere of the sun. It consists mostly of electrons and protons with energies of about 1 keV. The stream of particles varies in temperature and speed with the passage of time. These particles are able to escape the sun’s gravity, in part because of the high temperature of the corona, but also because of high kinetic energy that particles gain through a process that is not well-understood.
The solar wind creates the Heliosphere, a vast bubble in the interstellar medium surrounding the solar system. Other phenomena include geomagnetic storms that can knock out power grids on Earth, the aurorae such as the Northern Lights, and the plasma tails of comets that always point away from the sun.
Solar Wind Flow Pressure is something that is tracked daily by the Space Weather Prediction Center (SWPC) For example they display a nifty solar wind dashboard gauge on Space Weather Now that shows “dynamic pressure”:
Dynamic Pressure Dial:
Ranges from 0.1 to 100 nPa. The scale is log10 over the full range. If the density or speed data are missing, the arrow will not appear. The arrow will move to the location on the scale corresponding to the actual value of the latest 15 minute average of the Dynamic Pressure P of the solar wind. Dynamic Pressure is a function of speed and density.
David Archibald writes:
Robert Bateman’s graphic of the solar wind sent me in search of a longer time series. I found a longer one, and one that is a more accurate indication of the force that is pushing the galactic cosmic rays out from the inner planets of the solar system. It is the three month smoothed, 27 day average of the solar wind flow pressure. The data is from the Omniweb site.
The narrow downtrend channel that started in 2005 is quite evident. Before that it was trendless, and didn’t change with solar cycle amplitude. The volatility within the downtrend is much less than it was prior to 2005. Also evident is a big oscillation in 2004, which may be an artefact of a switch that changed the mode.
From this chart, solar activity is still falling until the downtrend channel is broken. As the solar wind takes a year to reach the heliopause, the Oulu neutron count will continue to rise for the next year. But just as the Earth’s atmosphere has shrunk, the heliopause will also be shrinking.
However this Archibald graph only shows a narrow slice of the entire data picture, Leif Svalgaard has an OMNI2 dataset that tracks back to 1963:
While we can indeed see the current downtrend since 1997, we have had periods before where the solar wind has been almost as low . Though NASA said last year “This is the weakest it’s been since we began monitoring solar wind almost 50 years ago.”.
There is an overall down trend since 1992, with a short plateau at the last solar max around year 2000-2004, followed by another downtrend starting about 2005.
In terms on the sun’s history (if it were compared to a day) we have about a microsecond worth of data out of that day on display above. So what conclusion, if any, can we draw from it? The only one I can see is it showing reduced solar activity, but nothing profound (in terms of the solar wind data we have) except that. We see a low period of similar amplitude around 1970, but it is noisier. The trend we’ve seen since 2005 is less noisy, which is inline with the quiet sun we have observed recently.
Let’s hope sol gets the magneto revved up again.
UPDATE: I had written to David Archibald, saying that “the broader data set to 1963 didn’t agree with your conclusions”, and he wrote back within about 15 minutes and provided a new graph:
Anthony, Agreed, and thankyou.
I went back to find the larger data set, as follows:
It is evident that the longer picture is more complicated. The correlation with solar minima and maxima is quite poor. Activity did not recover into Solar Cycle 23.
Yours sincerely,
David Archibald
So now we have all the makings of a good debate.
RACookPE1978 (13:34:25) :
Am I allowed to disagree? 8<)
Of course, if you then are willing to learn more about where you disagree.
If the sunspots (from an odd or even cycle) overlap on a time axis, so much the BETTER.
Please explain that in detail [that befits CAPITAL letters]
If and when they overlap – and it is an unknown “if” (at least right now (hint, hint))
This is not an if as it has been known for centuries that they overlap. A good representation of the overlap can be seen on page 7 of http://www.leif.org/research/Most%20Recent%20IMF,%20SW,%20and%20Solar%20Data.pdf where each cycle is given a different color. On page 7 you can see the current minimum in more detail.
that we don’t know now. Including skipped cycles (where opposing cycles cancel each other somehow), overlapping cycles (high intensities?) and the differences between the intervals between cycles.
We have measured the polarities directly for a hundred years.
On the other hand, if you don’t look, you won’t find anything other than what you already know you want to see. Or don’t want to see. 8<)
Oh, we look, but we also apply a bit of reason, common sense, and wonder [just in case something extraordinary happens].
Leif Svalgaard (14:13:26) :
A good representation of the overlap can be seen on page 4 [four] of http://www.leif.org/research/Most%20Recent%20IMF,%20SW,%20and%
Dr. Svalgaard
Leif Svalgaard (13:24:12)
The kinetic energy of the CRs is given by the fully relativistic formula
Ek = mc^2((1-(v/c)^2)^(-1/2)-1)
Using the formula for relativistic kinetic energy
assuming fast solar wind in corona of 600km/s
Kinetic energy of proton would be 3*10E-16 Joules
Kinetic energy of electron would be 1.6*E-19 Joules
and corona density (somewhere in the middle) of 1*10E-12 kg/m3
this would give 6*10E14 protons/m3 (neglecting electrons mass ~2000 smaller)
If it is assumed that corona temperature for that particular region is 1*10E6
assuming specific heat for proton is same as for hydrogen 1.43*10E-2
in a collision between proton and electron
to raise temperature by 1K of 1m3 of corona it is needed energy of 1.43*10E-14 J
for 1*10E6 K it is required 1.43*10E-8 J
If amount of kinetic energy loss to heat is equally shared between proton and electron assuming balanced numbers, and electron retains 1/2 of its energy
then number of collisions required is 4.36*10E4/m3
Since number of protons is calculated to be 6*10E14 protons/m3
then only small fraction of 7.3*10E-11 or 70 protons per 10,000,000,000 (70 per American 10 billion) have to be involved in such collisions to heat up corona to 1 million degree Kelvin.
It is more than likely that there is one or more errors in my calculations but nevertheless principle is there.
You may dispute possibility of proton electron collisions, but under a specific conditions that could happen in a strong magnetic field, which we may discuss elsewhere or at some other time.
If you are tempted to redo calculations and change some of the assumptions I would like to see final (and properly calculated) result.
I have had many a great laugh from this series and have learned an unimaginable amount about so many topics. I thank Leif for his dedication to his field (and many others closely associated) and his willingness — sometimes dedication — to teach us, even his peers, his knowledge about the sun. I am so grateful that few “incorrect” statements go unanswered and those about which there is strong disagreement, well, we can do the lady(ish?) and gentlemanly thing by agreeing to disagree. Even though a non-scientist (but someone who has loved science forever), I now have folders of great post-graduate seminar material on solar physics (and assorted other topics). Fools will not be suffered gladly on wuwt. And that is good news from my perspective; forget vinegar and honey; leave in the respect.
One other contribution of Leif’s that I think is more important than we may understand at this moment is: If we can get off this fixation with the sun or the sun’s spots or whatever as THE CAUSE of Earth’s climate changes, we can turn more attention to the interaction of oceans, atmosphere, earth’s typography and plate tectonics, winds, large ocean and atmospheric waves, modern milankovitch cycles, and many more actors with the insolation (do I have the term right?) from the sun. What drives what when?
IMO, our biggest thinking task is learning to adjust to cold, inventing ways to prevent glaciers and ice sheets from growing “too large”, and developing crops/trees/grasses that will grow in cooler climes. Worry about melting Arctice sea ice!?!? We worry about the Little Ice Age (Maunder Minimum in sun spots) and the Dalton Minimum (compared to today and our lazy sun) when these were just little blips down in temperature compared to the big picture. It blows my mind everytime I notice that we are in a brief, slightly warm lull in an ice age. The science of climate has many larger issues with which to grapple. Anthropogenic global warming, indeed. Bring it on.
M. Simon (06:12:05) :
It is not only the solar wind that is reduced. Wind in the USA is declining.
The culprit of course? Global Warming. We are doomed.
It’s another Mannistic Hockey Stick… Winds are well, we are not so well… 🙂
I did, a while back, for my own entertainment, a back-of-envelope calculation of how much energy was being dumped on the Earth by the Solar Wind. It turned out to be not much; rather like the Not Much due to TSI variation, or Magnetic variation, or Cosmic Ray variation.
However, I begin to think that these several “not muches” add up to a great deal, especially when their possible impact on Albedo – which really does not take much change to have a Big Impact on received Solar Output.
We must spend more effort studying the Sun and the Solar-Earth interaction and the Earth’s Albedo.
vukcevic (15:26:45) :
“The kinetic energy of the CRs is given by the fully relativistic formula Ek = mc^2((1-(v/c)^2)^(-1/2)-1)”
Using the formula for relativistic kinetic energy
assuming fast solar wind in corona of 600km/s
Kinetic energy of proton would be 3*10E-16 Joules
For v much smaller than c, the formula reduces to:
Ek = mc^2(1+v^2/c^2/2-1) = mc^2(v^2/c^2/2) = mv^2/2 (or classical formula) which for m = 1.7E-27 kg and v = 600,000 m/s = 6E5 gives Ek = 3E-16 J. No need to complicate it with relativistic formula.
For the rest, many of the conditions you invoke do not apply, e.g. the specific heat. Instead of me spending many pages on explaining this I’ll refer you to http://solarphysics.livingreviews.org/open?pubNo=lrsp-2006-1&page=articlesu17.html and surrounding text. Collisions are indeed rare in the corona: typically a proton travels 1000 km before colliding with another particle. The proton-electron collision is a red herring. See in particular the following sections:
3.4 The failure to heat chromosphere or corona by collisions
4.3 Breakdown of classical electron transport in the corona
6.9 Plasma heating (cooling) by wave absorption (emission)
Pamela Gray @20:32:24,
I agree with you. Current Solar activity is business as usual, over long periods of time; it is quite unusuial for the past 100 years – the period over which man-kind has supposedly affected climate.
Perhaps the tides are turning, Mr. Canute. 🙂
Robert Wood (16:52:39) :
However, I begin to think that these several “not muches” add up to a great deal, especially when their possible impact on Albedo
Several ‘nor muches’ still ain’t much. The albedo is the most important parameter in the climate business, but is, of course, a chicken/egg question as the albedo regulates climate which in turn determines the albedo. The various attempts to explain albedo variations from extraterrestrial causes have not been convincing.
vukcevic (15:26:45) :
In case you don’t want to wade through that highly technical paper [and it must be so, this ain’t easy], I’ll quote an importnat passage:
“Kinetic processes prevail in the solar corona and solar wind. Since the plasma is tenuous, multi-component, non-uniform, and mostly not at LTE (Local Thermodynamic Equilibrium) or collisional equilibrium conditions, multi-fluid theories or kinetic physics are required for an adequate description of many coronal and solar wind phenomena. The coronal plasma is stratified and turbulent, and strongly driven by the underlying photospheric magnetoconvection, which is continuously pushing around the magnetic field lines reaching out into the corona. Thus the field contains ample free energy for driving plasma macro- and micro-instabilities. Consequently, magnetohydrodynamic as well as kinetic plasma waves and associated wave-particle interactions are expected to play a major role.
Certainly, Coulomb collisions also matter, which are kinetically described by the Fokker–Planck operator (see, e.g., Montgomery and Tidman, 1964). However, excitation, scattering and absorption of waves, either of fluid or kinetic type, will dominate over collision effects. The consequences for the velocity distribution function (VDFs) are often described by a quasilinear diffusion operator involving the wave spectra. The key problem then is to understand the transport properties of the weakly collisional corona (and solar wind), which requires consideration of multiple scales, spatial non-uniformity and most likely also temporal variability.
The solar wind consists of electrons, protons, alpha particles and heavy ions. Kinetic plasma physics deals with their collective behaviour as a statistical ensemble. Space-borne particle spectrometers enable us to measure the composition and three-dimensional velocity distribution functions (VDFs) of the particles. The Vlasov/Boltzmann kinetic plasma theory provides the adequate means for their theoretical description. Key issues of kinetic physics are to address the coronal origin and acceleration of the wind and the spatial and temporal evolution of the particles’ VDFs. They are shaped through the forces of the Sun’s gravitational field, the average-macroscale and fluctuating-mesoscale electric and magnetic fields of interplanetary space, and through multiple microscale kinetic processes like binary Coulomb collisions and collective wave-particle interactions. Although, coronal expansion is irreversible, the solar wind microstate carries distinct information about the coronal plasma state in the source region, and thus in situ measurements allow for inferences and provide a kind of remote-sensing diagnosis of the coronal plasma.”
Leif Svalgaard @20:55:58
I agree with your post mostly … but … we now have low solar (wind) pressure but it is at a solar minimum. There does appear to be several indicators of some kind of change in 2005.
Leif Svalgaard @17:23:48
The coronal plasma is stratified and turbulent,
Please explain how it can be calm (stratified) and turbulent at the same time. Sorry, doesn’t work.
As to the Albedo, it appears we borh agree this is THE MOST important factor for Earth’s climate. Yet it appears to be ignored, or assumed constant, by the AGWERS.l
I’ve never read anything about this, but, obviously, the Sun must be ejecting as many electrons as positive charges, otherwise it would build up a ginormous electrostatic charge.
I have wondered about the type of data we are getting from Voyager I & II leaving the solar system.
Are either one of them far enough out yet to get a reading on the local Galactic conditions free from the influence of the Sun?
Your comment Leif: “possibly because of a genuine decrease of the galactic flux in the solar neighborhood” make me wonder if we are in a position to follow which way those conditons are moving…up or down.
Robert Wood (18:08:59) :
That change began shortly after 1991.
Coincident to L&P’s finding.
They both stand independent of the Solar Cycles.
Do they have a common cause?
Are they related?
Does one cause the other, and if so, which one?
Why these two things, and not three or four?
This is what I have been thinking and suspecting for a while now: some of the things that affect Earth, its climate, and the space we live in have such long cycles that at best our data sets have a “snapshot” view of them, even if they go back for 40 or 50 years. For example: this July 4th, America will be 233 years old. If in 1776 we’d had satellites up in space, and the science to support them, we’d have 20 cycles worth of top-notch data. That sounds impressive, and on one scale would be helpful, but over the life cycle of a star that is billions of years old (and still has a few billion to go) even that is not all too impressive. Or take the PDO (please!) which has a cycle of 20-30 years. Average 25 for that and you have 4 cycles in a century. So in that we’d have 9 cycles of top-notch data if your science in 1776 could compare to now. Again though, nine cycles out of how many thousands of years that it has been around doing its thing while humanity thought it had accomplished something by stacking stones on top of each other in something we call the Pyramids. Makes one reconsider things.
Here is an interesting plot:
http://www.leif.org/research/Alfvenic-Mach-Number.png
Just as for sound waves in air, there is a concept of ‘supersonic’ flow [an airplane going at Mach 2, for instance] in the solar wind as well. The speed with with hydrodynamic waves can propagate is called the Alfven speed [after Hannes Alfven who first figured this out]. In the solar wind this speed is about 40 km/s. Since the solar wind is moving at 400 km/s which is 10 times the Alfven speed we can say that its Alfvenic Mach number MA is 400/40 = 10. With the units commonly used in solar wind studies MA can be computed from MA = V * sqrt(n) / (20 * B), with speed V in km/sec, n density in protons per cubic centimeter, and magnetic B in nanoTesla, and is shown in the Figure as the pink curve. As these parameters vary over time and with the solar cycle, the Alfvenic Mach number, MA, will also as shown in the Figure. You can see a clear solar cycle variation, with MA being lowest at solar maximum and largest at solar minimum. One can formalize this relationship as shown by the blue formula: MA = 10/[0.6595 + 0.0539 sqrt(Rz)], where Rz is the [Zurich] Sunspot Number. This relationship is derived from a least squares fit of the data before 2002. The fit during 1993-1994 is less good because of large data gaps [70% of the data missing – due to no satellite being in the solar wind at most of that time interval]. Using the relationship one can with good approximation calculate the Alfvenic Mach Number from the Sunspot number. We do that now for the whole period up tyo present, the blue curve continuing as would expect the observations to ‘cling’ to the blue curve just as the pink curve did. This is clearly not the case, the observation since 2002 being plotted in red and clearly falling below the expected values.
Several hypotheses can now be made:
1) the relationship somehow changed. This is unlikely as those things are fundamental plasma properties that eventually are derived from solar magnetism.
2) since the observed values are too low, it could be that the magnetic field, B, is too high for some reason as it occurs in the denominator. The excellent agreement between B measured by spacecraft and that derived from geomagnetic activity argues against B being wrong.
3) the solar wind speed V could be too low. The excellent agreement between V measured by spacecraft and that derived from geomagnetic activity argues against V being wrong.
4) the density, n, [which determines the flow pressure – hence this comment being on topic] could be too low
5) since the expected MA [blue line] depends on the sunspot number in the denominator, it will appear too large [hence the red curve too low] if the sunspot number is wrong [too low] from 2002 onwards
6) something completely different or multiple errors just conspiring to fool us
My assessment is that either (4) or (5) or both are the culprits. The good news is that we are beginning to understand the physics of all this to the point where we can demand that everything must fit, so such discrepancies become important clues rather than just annoying noise.
Robert Wood (18:19:16) :
“The coronal plasma is stratified and turbulent”
Please explain how it can be calm (stratified) and turbulent at the same time. Sorry, doesn’t work.
Does! because these two properties are on different length scales: ordered on large scales and turbulent on small scales, like a stormy sea seen from 40,000 ft.
Robert Wood (18:25:21) :
I’ve never read anything about this, but, obviously, the Sun must be ejecting as many electrons as positive charges, otherwise it would build up a ginormous electrostatic charge.
Yes, this was realized as far back an in 1919 by Lindeman and was is still of fundamental importance: the solar wind is electrically neutral. One argument often used is that electrons are so much lighter than protons that they escape easier from the Sun. This process would set up what is known as a Pannekoek-Rossland electric field which would grow so strong as to pull the protons up too and thereby neutralize the field.
rbateman (18:41:24) :
I have wondered about the type of data we are getting from Voyager I & II leaving the solar system.
Are either one of them far enough out yet to get a reading on the local Galactic conditions free from the influence of the Sun?
I showed earlier a plot of the flow pressure from the Voyagers http://www.leif.org/research/Solar-Wind-Dynamic-Pressure-Voyager.png and you can see that they observe the expected solar cycle variation [smallest pressure at solar max]. Also at the right the pressure after having left the heliosphere. But there is a large region outside the termination shock filled with ‘old’ solar wind so they are not yet in true interstellar medium and will not be so for another 50 years or so, at which time their reactors will have run down and we’ll have lost radio contact.
Your comment Leif: “possibly because of a genuine decrease of the galactic flux in the solar neighborhood” make me wonder if we are in a position to follow which way those conditons are moving…up or down.
The argument for a decrease is here: http://neutronm.bartol.udel.edu/reprints/2007bieber.pdf and looks good to me.
If I remember correctly, one of the theories regarding the trigger for ice ages is an upsurge in cosmic radiation increasing cloud cover. One counter argument was that there was no known causal factor for a cosmic ray increase that would account for the cyclical regularity seen in ice age periods. The data here makes me wonder; perhaps the cosmic ray theory was correct, but instead of an increase in cosmic rays, it was merely an increase in cosmic rays reaching Earth? We do know that the sun has cycles, though we’ve only seen shorter term ones. Could a decline in solar wind pressure by a cyclical event of roughly 100,000 years, and be the trigger for ice ages?
Just some wild guesswork on my part.
Leif Svalgaard (12:53:27) :
“As I have mentioned before, humans [and I think almost any animal] have a tendency to believe false negatives because this has strong survival benefits [‘better be safe than sorry’]. The problem comes when crowd psychology takes over and we follow the doom sayers over the edge.”
And that in a nutshell sums up the AGW movement perfectly IMHO.
Nice one Leif!
Dr. Svalgaard
Thanks for the link, I will follow it up. I have seen number of papers considering heating by wave absorption.
a) uncertainty about existence of waves of sufficient energy required
b) energy transfer by wave absorption is proportional to the density, conflict with the corona’s temperature gradient.
On unrelated topic, I have come across this:
Average properties of the solar wind at 1 AU. (from ‘Introduction to space physics’ p.93 ch. 4.2 , Kivelson and Russell, 1995, Google books)
Proton density = 6.6/cm3 , Electron density =7.1/cm3 .
Since proton count (at various energy levels) varies on any time scale, are these values a reasonable long term representation (electron excess of approx 7.5% ) ?
There is also a number for protons, but not for the electrons flux, if the speed is same would the electron flux be in the above proportion?
Any other, more up to date, average numbers for average density or flux?
Thanks.
Leif:
After reading the 2007 bieber pdf, the only thing I would consider is that both the detector temp and the increased hit rate in concert led to a higher rate of decline.
I know that most electronics work much better at lower temps, and it the neutron detector is recording more, it’s degrading faster.
A new tube would record at a greater rate at such low temps.
It would get used up faster (as the paper seems to cover).
Since tubes have been changed over time, that still wouldn’t make the entire record fall at the given rate, UNLESS… the replacement tubes were sitting down there under increased exposure even though not used.
That’s the last piece I can think of. When are the replacement tubes made?
At the same time as the 3 originals or on an as-needed basis? Where are they kept?
I’m trying hard to take a bite out of the 8%, but I know you scientists are like the Silicon Valley Engineers… a rare day when one can out think them.
CJ (23:38:40) :
Or the Ice Ages are the result of an overwhelming of the Solar Wind etc by a cloud of concentrated GCR’s. Making a mess out of things and polluting the heck out of the Solar System which ionizes and drags a portion of the cloud with it. Smogs it up, but that should leave tattletale signs in the geologic record. As in there’s no such thing as a perfect crime.
“But there is a large region outside the termination shock filled with ‘old’ solar wind so they are not yet in true interstellar medium and will not be so for another 50 years or so, at which time their reactors will have run down and we’ll have lost radio contact.”
Wouldn’t you know it? Murphy’s Law prevents exiting the Stellar Medium in good order. Good project for an ion engine.
From spaceweather.com, about Noctilucent clouds:
“Even deeper hypnosis is in the offing. There is a well-known correlation between noctilucent clouds and the solar cycle: NLC activity tends to peak during years of solar minimum, possibly because low solar activity allows the upper atmosphere to cool, promoting the growth of ice crystals that make up the clouds. With a century-class solar minimum underway, the stage is set for NLCs.”