December 23, 2009: The solar system is passing through an interstellar cloud that physics says should not exist. In the Dec. 24th issue of Nature, a team of scientists reveal how NASA’s Voyager spacecraft have solved the mystery.
“Using data from Voyager, we have discovered a strong magnetic field just outside the solar system,” explains lead author Merav Opher, a NASA Heliophysics Guest Investigator from George Mason University. “This magnetic field holds the interstellar cloud together and solves the long-standing puzzle of how it can exist at all.”
Right: Voyager flies through the outer bounds of the heliosphere en route to interstellar space. A strong magnetic field reported by Opher et al in the Dec. 24, 2009, issue of Nature is delineated in yellow. Image copyright 2009, The American Museum of Natural History. [larger image]
The discovery has implications for the future when the solar system will eventually bump into other, similar clouds in our arm of the Milky Way galaxy.
Astronomers call the cloud we’re running into now the Local Interstellar Cloud or “Local Fluff” for short. It’s about 30 light years wide and contains a wispy mixture of hydrogen and helium atoms at a temperature of 6000 C. The existential mystery of the Fluff has to do with its surroundings. About 10 million years ago, a cluster of supernovas exploded nearby, creating a giant bubble of million-degree gas. The Fluff is completely surrounded by this high-pressure supernova exhaust and should be crushed or dispersed by it.
“The observed temperature and density of the local cloud do not provide enough pressure to resist the ‘crushing action’ of the hot gas around it,” says Opher.
So how does the Fluff survive? The Voyagers have found an answer.
“Voyager data show that the Fluff is much more strongly magnetized than anyone had previously suspected—between 4 and 5 microgauss*,” says Opher. “This magnetic field can provide the extra pressure required to resist destruction.”
Above: An artist’s concept of the Local Interstellar Cloud, also known as the “Local Fluff.” Credit: Linda Huff (American Scientist) and Priscilla Frisch (University of Chicago) [more]
NASA’s two Voyager probes have been racing out of the solar system for more than 30 years. They are now beyond the orbit of Pluto and on the verge of entering interstellar space—but they are not there yet.
“The Voyagers are not actually inside the Local Fluff,” says Opher. “But they are getting close and can sense what the cloud is like as they approach it.”
The Fluff is held at bay just beyond the edge of the solar system by the sun’s magnetic field, which is inflated by solar wind into a magnetic bubble more than 10 billion km wide. Called the “heliosphere,” this bubble acts as a shield that helps protect the inner solar system from galactic cosmic rays and interstellar clouds. The two Voyagers are located in the outermost layer of the heliosphere, or “heliosheath,” where the solar wind is slowed by the pressure of interstellar gas.
Voyager 1 entered the heliosheath in Dec. 2004; Voyager 2 followed almost 3 years later in Aug. 2007. These crossings were key to Opher et al‘s discovery.
Right: The anatomy of the heliosphere. Since this illustration was made, Voyager 2 has joined Voyager 1 inside the heliosheath, a thick outer layer where the solar wind is slowed by the pressure of interstellar gas. Credit: NASA/Walt Feimer. [larger image]
The size of the heliosphere is determined by a balance of forces: Solar wind inflates the bubble from the inside while the Local Fluff compresses it from the outside. Voyager’s crossings into the heliosheath revealed the approximate size of the heliosphere and, thus, how much pressure the Local Fluff exerts. A portion of that pressure is magnetic and corresponds to the ~5 microgauss Opher’s team has reported in Nature.
The fact that the Fluff is strongly magnetized means that other clouds in the galactic neighborhood could be, too. Eventually, the solar system will run into some of them, and their strong magnetic fields could compress the heliosphere even more than it is compressed now. Additional compression could allow more cosmic rays to reach the inner solar system, possibly affecting terrestrial climate and the ability of astronauts to travel safely through space. On the other hand, astronauts wouldn’t have to travel so far because interstellar space would be closer than ever. These events would play out on time scales of tens to hundreds of thousands of years, which is how long it takes for the solar system to move from one cloud to the next.
“There could be interesting times ahead!” says Opher.
To read the original research, look in the Dec. 24, 2009, issue of Nature for Opher et al’s article, “A strong, highly-tilted interstellar magnetic field near the Solar System.”
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Leif Svalgaard (10:22:48) :
tallbloke (10:14:46) :
Why?
A one word question gets a one word answer:
Because.
Which are both meaningless in this context.
I for one share your optimism for human knowledge Leif. If we stay sharp and keep learning, we’ll find out more than we already have.
Niels A Nielsen (12:49:23) :
Is that Voltaire? I thought it was my countryman – and your excountryman – Ludvig Holberg.
It was Holberg, you are right. Wasn’t Holberg called the ‘Danish Voltaire’? incorporating many of the same ‘tricks’ and style in his plays as Voltaire. In any event, let’s give credit where credit is due.
Its very obvious that the level of solar understanding is weak and that no particular stream can claim the “science is settled”.
There is a long way to go before we discover the actual driver/s of the Sun and our climate, it is indeed a most interesting time to be alive.
Dr. Svalgaard: “The solar wind accelerates because it is being heated and [somewhat counter-intuitively] because its outflow is being restricted by gravity [see deLaval nozzle http://en.wikipedia.org/wiki/De_Laval_nozzle ].”
The solar wind is being “heated” continually beyond the corona?
The “heating” hypothesis has been generally discredited by falsifying observations & measurements. So, no, that argument doesn’t work.
But if there is a recent scientific paper (within the last decade) that makes such a claim, I’m open to reading it.
Now, the Sun’s gravity does drop off the farther away from the Sun, which might allow for acceleration of solar wind, but likely that doesn’t account for the amount of acceleration observed & measured. But if there is a scientific paper that makes such a claim, I’m open to read it.
As for the de Laval nozzle hypothesis, where is the equivalent location distant from the surface of the Sun where this analogous de Laval nozzle structure is present?
If the equivalent of the de Laval nozzle is located somewhere in the vicinity of the corona (even at the outward edge of the corona) there is acceleration at the point of the nozzle, but the velocity quickly falls off after the gas leaves the nozzle (this is not analogous to the behavior of the solar wind).
See diagram in the link below from de Laval nozzle Wikipedia entry cited above:
http://en.wikipedia.org/wiki/File:Nozzle_de_Laval_diagram.svg
What physical conditions or structure in the solar wind has an analogous structure to a de Laval nozzle? Have there been any specific observations & measurements that support this hypothesis?
Again, I’m open to reading a scientific paper that makes such a claim, but without a scientific paper supporting the contention, it comes across as a mere hypothesis or worse, simple speculation.
Dr. Svalgaard: “…electric fields [which BTW can’t exist in a space plasma, as you have been told numerous times].”
Actually, Dr. Svalgaard has previously acknowledged the presence of electric fields in space plasma.
Dr. Svalgaard: “Electric currents are the cause of all interesting phenomena involving plasmas and are created locally by movement of said plasma across an existing magnetic field.”
Dr. Svalgaard: “…there can be no electric fields in a plasma except in situations where [for very brief periods] the magnetic field is changing rapidly due to movements of the plasma…In such situations, the electric fields are almost instantly shorted out in an explosion [solar flare, aurora, magnetic storms, etc].”
Dr. Svalgaard contradicts himself and I suggest there are Electric Double Layers, aka “magnetic reconnection” (a source of electric currents in space plasma that Dr. Svalgaard previously specifically acknowledged), that while unstable, therefore, not long lasting (electrical phenomena are subject to instabilities), I suggest in certain circumstances and physical conditions are more long lasting than Dr. Svalgaard is willing to admit.
There have been electric fields observed & measured in the solar wind, the current sheet within the solar wind has been observed & measured to have an electric field and Electric Double layers have been observed & measured in the solar wind.
“Field line merging at the heliospheric current sheet (HCS) and the resulting disconnection of heliospheric magnetic field (HMF) lines from the Sun, has been controversial. The SWEPAM and MAG experiments on ACE have now obtained the first direct evidence for such merging and disconnection from the Sun. As illustrated by the figure on the left above, reconnection at the HCS should create closed field lines sunward and disconnected (from the Sun) field lines anti-sunward of the reconnection site.”
http://www.srl.caltech.edu/ACE/ACENews/ACENews88.html
See the diagram at the top left of the link for a schematic of a Electric Double Layer, aka “magnetic reconnection”, within the solar wind between the Sun and the Earth.
See, also, “Prolonged Reconnection at an Extended and Continuous X-line in the Solar Wind”:
“Magnetic reconnection [aka Electric Double Layers] is commonly invoked to explain a variety of space, solar, astrophysical and laboratory plasma phenomena. It has long been debated whether reconnection is fundamentally patchy in space and time or if, instead, it can occur in a quasi-stationary manner over an extended region in space. Direct evidence that reconnection commonly occurs in the solar wind is found in ACE observations of jetting Alfvnic plasma flows confined to magnetic field reversal regions. Multi-spacecraft measurements of such jetting plasma flows, known as reconnection exhausts, have suggested that they originate from quasi-stationary reconnection at extended reconnection sites (X-lines) in the solar wind.”
http://www.srl.caltech.edu/ACE/ACENews/ACENews105.html
(By the way, the ACE news release archive has many interesting reports.)
So, it would seem that not only does Dr. Svalgaard contradict himself regarding the presence of electric currents in space plasma, but, also, that the ACE satellite probe’s in situ observations & measurements contradict Dr. Svalgaard’s assertion about Electric Double Layers, aka, “magnetic reconnection”, being only a transient space phenomenon.
So, isn’t it possible that Electric Double Layers are present in deep-space structures, too, including the interface where the magnetized plasma cloud comes into contact with the solar heliosphere, which this “Watts Up With That?” post discusses?
Only continued space exploration and in situ satellite probes launched farther into the vast distances of space can determine for sure — interesting times we are living in, indeed.
Niels A Nielsen (12:49:23
Leif (05:50:03): “Your arguments remind me of Voltaire’s proof that you are a stone: “a stone cannot fly, you cannot fly, ergo you are a stone”.
Is that Voltaire? I thought it was my countryman – and your excountryman – Ludvig Holberg.
I was expecting the ‘poster’ to whom this rather inappropriate comment was directed, may have replied by quoting Descartes with “Je pense donc je suis” or the more familiar “Cogito, ergo sum”, but it appears as a wise man always does, he responded by terminating the exchange with a polite expression of thanks and appreciation.
James F. Evans (13:37:18) :
http://en.wikipedia.org/wiki/File:Nozzle_de_Laval_diagram.svg
What physical conditions or structure in the solar wind has an analogous structure to a de Laval nozzle?
The heating of the solar wind causes it to expand. Gravity tried to hold it back, that is the constriction you see in the diagram, but as gravity gets weaker with distance, the constriction is gradually removed, that is the widening of the nozzle. The result, as the diagram shows [look at the blue curve] is an acceleration to supersonic speed that continues with increasing distance [look at the blue curve]. This is textbook stuff that was figured out in the late 1950s and early 1960s.
So, it would seem that not only does Dr. Svalgaard contradict himself regarding the presence of electric currents in space plasma, but, also, that the ACE satellite probe’s in situ observations & measurements contradict Dr. Svalgaard’s assertion about Electric Double Layers, aka, “magnetic reconnection”, being only a transient space phenomenon.
I thought we have gone over this ad nauseam. I have stated many times that electric currents exists in space, created locally by plasma moving across magnetic fields or when opposite magnetic fields are forced together by plasma movements. This is old hat.
Double Layers are very thin and the electric field in them very localized. The discharge of the double layer field creates the current. Unless the double layer is being continually replenished by plasma moving in magnetic fields, they dissipate.
So, isn’t it possible that Electric Double Layers are present in deep-space structures, too, including the interface where the magnetized plasma cloud comes into contact with the solar heliosphere, which this “Watts Up With That?” post discusses?
Certainly, as they are generated by moving neural plasma pressing opposite field lines together resulting in reconnection. This is also old hat.
Your problem is that you fail to grasp that all electric fields and currents are generated by plasma moving in magnetic fields. A ‘genuine’ electric field caused by large-scale charge separation [and how do you get that without a magnetic field?] will short itself out immediately.
I’m getting tired of beating this old horse. You ought to have learned it by now.
REPLY: “…continually replenished by plasma moving in magnetic fields”… Ditto that, it is a simple generator. Our earthly mechanical electrical generators are conductors moving through a magnetic field. Plasma is the moving conductor in this case.- Anthony
Tune for the evening.
Help I’m a rock!
Frank Zappa and the Mothers of Invention “Freak out!” 1967ish
Scientific discussion is a process of give and take and some statements are more precise and/or more accurate than others (no one has all the answers) — discussion allows for a shake out of statements and arguments, many times improving the understanding for both the maker of statements and, also, those pointing out the errors and vice versa.
That is why collaboration and cooperation are important in science — multiple perspectives add to the scientific process.
This is a good thing.
Evans (02:56:55) : “This sounds a bit like Schrödinger’s cat thought experiment, often described as a paradox: The cat can not be both dead and alive at the same time. A physical force is either present or not.”
“Thought experiments” are glorified hypothesis.
(I’m somewhat chagrined that I referred to a “thought experiment, myself.)
Empirical science depends on actual observations & measurements, preferably in controlled, repeatable experiments, but often the observations & measurements are in situ (hopefully repeatable), yet still these in situ observations are superior to mere “thought experiments”.
Dr. Svalgaard: “The [electric] field depends on the frame of reference so can be both present and not depending on the frame.
Demonstratably false.
“Frame of reference” is code for human perspective or perception: “thought experiment” if you will.
But human perception, even more so imagninary perception, is notriously unreliable in describing and explaining physical reality.
That’s why empirical science uses “thought experiments”, aka hypothesis, as a starting point, not as a basis for drawing solid scientific conclusions.
To demonstrate:
“The [electric] field depends on the frame of reference so can be both present and not depending on the frame.”
Electric fields in space are only observable or verifiable by satellite in situ probes that pass through the electric field.
Those probes are independent of frame of reference, they either detect the presence of an electric field or not. At any given time and location there is only one physical reality with a set of attendant specific physical conditions.
Imaginary human frames of reference have no relevance to a satellite probe’s in situ detection of an electric field.
If this was not so, then there would be “multiple realities”.
Empirical science abhors the idea of “multiple realities” at an identical time and location. Indeed, the veracity and reliability of empirical science depends on the concept of only one physical reality.
So, the claim that an electric field can be both present and detectable in situ and also not present and, therfore, undetectable at the same identical time and location depending on human frame of reference is pseudo-science.
The claim only serves to muddy the waters and is an affront to empirical science.
James F. Evans (13:37:18) :
http://en.wikipedia.org/wiki/File:Nozzle_de_Laval_diagram.svg
“What physical conditions or structure in the solar wind has an analogous structure to a de Laval nozzle?”
With all due respect, it sure would be nice if a scientific paper(s) was provided which supports the explanation provided, as I previously indicated I would be open to reading any scientific papers cited as authority.
After all, if this is “textbook stuff that was figured out in the late 1950s and early 1960s.”, then surely there would be scientific papers specifically citing this de Laval nozzle hypothesis (even recent papers citing previous authority for the proposition).
Understanding of solar wind dynamics has come a long way from the 50’s and early 60’s.
Dr. Svalgaard: “I thought we have gone over this ad nauseam. I have stated many times that electric currents exists in space, created locally by plasma moving across magnetic fields or when opposite magnetic fields are forced together by plasma movements. This is old hat.”
Yes, indeed, you have, that’s why I was surprised when you responded: “…electric fields [which BTW can’t exist in a space plasma, as you have been told numerous times].”
And I was surprised when you stated previously in this comment thread:
Leif Svalgaard (12:52:08) :”There are no electric fields in the plasma.”
I trust I won’t see the above quoted statement, again.
Dr. Svalgaard: “Unless the double layer is being continually replenished by plasma moving in magnetic fields, they dissipate.”
See, again, “Prolonged Reconnection at an Extended and Continuous X-line in the Solar Wind”:
“Magnetic reconnection [aka Electric Double Layers] is commonly invoked to explain a variety of space, solar, astrophysical and laboratory plasma phenomena. It has long been debated whether reconnection is fundamentally patchy in space and time or if, instead, it can occur in a quasi-stationary manner over an extended region in space. Direct evidence that reconnection commonly occurs in the solar wind is found in ACE observations of jetting Alfvnic plasma flows confined to magnetic field reversal regions. Multi-spacecraft measurements of such jetting plasma flows, known as reconnection exhausts, have suggested that they originate from quasi-stationary reconnection at extended reconnection sites (X-lines) in the solar wind.”
http://www.srl.caltech.edu/ACE/ACENews/ACENews105.html
It would seem that, indeed, there are instances where “…the double layer is being continually replenished by plasma moving in magnetic fields…”.
Dr. Svalgaard: “Double Layers are very thin and the electric field in them very localized.”
But electric phenomenon are scale independent and, so, the size of the Double Layer can vary greatly. So, while the Double Layer is proportionately thin and the electric field is proportionately localized, if the overall scale of the Double Layer is large, a proportional increase in the thickness of the Double Layer and a proportional increase in the area of the electric field should be observed.
Dr. Svalgaard: “Certainly, as they [Electric Double Layers] are generated by moving neural plasma pressing opposite field lines together resulting in reconnection. This is also old hat.”
Yes, I agree, it is “old hat”, but I was stating that for the benefit of other readers, who may not be familiar with discussions on earlier posts.
Dr. Svalgaard: “Your problem is that you fail to grasp that all electric fields and currents are generated by plasma moving in magnetic fields.”
No, I have no problem with that.
What I have difficulty with is your answer to this question:
“Yes but what causes the existing magnetic fields?”
Leif Svalgaard (14:27:28) : “They have always been there.”
That’s an unsatifying answer. It doesn’t describe or explain in any meaningful fashion.
Science operates on the causation principle, namely: The job of Science is to describe & explain the “cause” of physical pehonenon.
“They [magnetic fields] have always been there.”, doesn’t answer that question.
James F. Evans (13:37:18) :
“Field line merging at the heliospheric current sheet (HCS) and the resulting disconnection of heliospheric magnetic field (HMF) lines from the Sun, has been controversial. The SWEPAM and MAG experiments on ACE have now obtained the first direct evidence for such merging and disconnection from the Sun. As illustrated by the figure on the left above, reconnection at the HCS should create closed field lines sunward and disconnected (from the Sun) field lines anti-sunward of the reconnection site.”
http://www.srl.caltech.edu/ACE/ACENews/ACENews88.
~
Thank you for the links. Very good info..
Leif Svalgaard (14:30:25) :
James F. Evans (13:37:18) :
The heating of the solar wind causes it to expand. Gravity tried to hold it back, that is the constriction you see in the diagram, but as gravity gets weaker with distance, the constriction is gradually removed, that is the widening of the nozzle. The result, as the diagram shows [look at the blue curve] is an acceleration to supersonic speed that continues with increasing distance [look at the blue curve]. This is textbook stuff that was figured out in the late 1950s and early 1960s.
Double Layers are very thin and the electric field in them very localized. The discharge of the double layer field creates the current. Unless the double layer is being continually replenished by plasma moving in magnetic fields, they dissipate.
~
James F. Evans (13:37:18) :
So, isn’t it possible that Electric Double Layers are present in deep-space structures, too, including the interface where the magnetized plasma cloud comes into contact with the solar heliosphere, which this “Watts Up With That?” post discusses?
~
Certainly, as they are generated by moving neural plasma pressing opposite field lines together resulting in reconnection. This is also old hat.
.. all electric fields and currents are generated by plasma moving in magnetic fields.
A ‘genuine’ electric field caused by large-scale charge separation [and how do you get that without a magnetic field?] will short itself out immediately.
I’m getting tired of beating this old horse. You ought to have learned it by now.
REPLY: “…continually replenished by plasma moving in magnetic fields”… Ditto that, it is a simple generator. Our earthly mechanical electrical generators are conductors moving through a magnetic field. Plasma is the moving conductor in this case.- Anthony
As always Dr S. thanks for your insights.
Speaking of generators and dead horses…can we freeze the generator? Or..slow it down just like our solar cycle?
Whilst the older brother and nephew were here, we started discussing just that. But I was sent off by a dryer buzzer and a google search for the temp of liquid hydrogen. Man you get back and the scenery all changes.
Tallbloke, no wonder why you think you are a rock, been listening to Zappa. Except for “Joes Garage,” not too familiar with Zappa. Oh yeah, watch out where the huskies go and don’t you eat know yellow snow. Oh know.
James F. Evans (16:23:08) :
“Empirical science abhors the idea of “multiple realities” at an identical time and location.”
Think of this thought experiment. You are on a boat moving with the water on a swift river. You pass by another man who is standing in the water. You both dip your hands in the water at the same place at the same instant. Your hand just goes right down without a splash, yet the other man’s hand creates a wake. Why? You are both in the same position at the same time. Is this a paradox?
Of course not. You just need to account for another variable, that being your instantaneous velocity relative to the water.
Leif Svalgaard (14:30:25) :
REPLY: “…Plasma is the moving conductor in this case.- Anthony
And, electric fields do not exist in a lossless conductor. I am assuming you are positing that the plasma is a very efficient conductor?
Bart (17:51:52) :
in reply to James F. Evans (16:23:08) :
electric fields do not exist in a lossless conductor. I am assuming you are positing that the plasma is a very efficient conductor?
Perhaps I should just let Bart’s word be the last on this. Evans is too far gone to argue with. [And we have already been over all that many times]. And the origin of primordial magnetic fields is indeed an unsolved problem.
Even Wiki has picked up the de Laval nozzle explanation:
“Parker showed that even though the sun’s corona is strongly attracted by solar gravity, it is such a good conductor of heat that it is still very hot at large distances. Since gravity weakens as distance from the sun increases, the outer coronal atmosphere escapes supersonically into interstellar space. Furthermore, Parker was the first person to notice that the weakening effect of the gravity has the same effect on hydrodynamic flow as a de Laval nozzle: it incites a transition from subsonic to supersonic flow.
Eugene Parker (1958). “Dynamics of the Interplanetary Gas and Magnetic Fields”. The Astrophysical Journal 128: 664.”
I’ll primarily let my comments speak for themselves, however, it is notable that Dr. Svalgaard has a propensity (at this website anyway) to make personal put downs against anybody who disagrees with him particularly if unable or unwilling to answer on the merits.
And regarding Wikipedia’s supposed endorsement of the de Laval nozzle hypothesis, the same Wikipedia article on solar wind referenced by Dr. Svalgaard goes on to write regarding Parker’s hypothesis:
“However, the acceleration of the fast wind is still not understood and cannot be fully explained by Parker’s theory.”
The Wikipedia article goes further:
“In the late 1990s the Ultraviolet Coronal Spectrometer (UVCS) instrument on board the SOHO spacecraft observed the acceleration region of the fast solar wind emanating from the poles of the sun, and found that the wind accelerates much faster than can be accounted for by thermodynamic expansion alone. Parker’s model predicted that the wind should make the transition to supersonic flow at an altitude of about 4 solar radii from the photosphere; but the transition (or “sonic point”) now appears to be much lower, perhaps only 1 solar radius above the photosphere, suggesting that some additional mechanism accelerates the solar wind away from the sun.”
To highlight: “…suggesting that some additional mechanism accelerates the solar wind away from the sun.”
http://en.wikipedia.org/wiki/Solar_wind
(Linked, so readers can check it out themselves — notice mention of Kristian Birkeland near the head of the article.)
As Paul Harvey said: “And that’s the rest of the story.”
Just thought readers would like to know.
James F. Evans (22:11:15) :
And regarding Wikipedia’s supposed endorsement of the de Laval nozzle hypothesis, the same Wikipedia article on solar wind referenced by Dr. Svalgaard goes on to write regarding Parker’s hypothesis:
“However, the acceleration of the fast wind is still not understood and cannot be fully explained by Parker’s theory.”
All that means is that the heating in the polar regions where the fast wind comes from is stronger than elsewhere [not too surprising since we have open magnetic field lines that can reconnect with underlying closed loops] and that the sonic point is not at a constant height. Parker assumed spherical symmetry for simplicity well knowing that that was only an approximation. The de Laval mechanism still stands as the means to achieve supersonic flow.
James F. Evans (16:23:08) :
“Yes but what causes the existing magnetic fields?”
Leif Svalgaard (14:27:28) : “They have always been there.”
That’s an unsatifying answer. It doesn’t describe or explain in any meaningful fashion.”
Quote from an earlier WUWT post:
Fabron (09:41:31) :
This is an extract from another discussion forum, where subject was considered ( lsvalgaard vs. vukcevic):
Einstein in his theoretical analysis of Brownian motion on the atomic and molecular level has shown, the kinetic theory implies that particle of different size will move differently; differentiation in velocity between heavy positive particles (protons and He ions) and super-light negative charged electron. If these differences exist even on micro scale, than the Maxwell’s equations (conservation of electric charge) imply that gradient of charge density at any point in space is directly related to the current density and vice versa. Electric current is nothing more than a spatial and temporal displacement of charge. So if there is temporal change in charge balance within a volume, than the current flowing into or out of a specified volume has to be equal the time-derivative of charge inside this volume ( div I = dq/dt ).
Conclusion: No initial magnetic field required, however appearance of the electric current will generate magnetic field.
http://wattsupwiththat.com/2009/09/01/new-mission-to-study-crossed-magnetic-streams-and-magnetic-portals/
What? Super*sonic* speed in space? Isn’t supersonic defined as a velocity faster than the speed of sound in a given medium?
Sound can’t travel in the vacuum of space, therefore there’s no such thing as a supersonic velocity in space.
Or is the solar corona supposed to be thick enough to transmit sound?
Gregg E. (00:39:55) : …Sound can’t travel in the vacuum of space…
Can it travel in the vacuum of a forest, Gregg?
Leif Svalgaard (22:56:03) :
“……….not too surprising since we have open magnetic field lines that can reconnect with underlying closed loops………”
If this is an illustration of what Dr. Leif Svalgaard has in mind
http://sprg.ssl.berkeley.edu/~tohban/nuggets/images/14_flare_model.gif
then I suggest that George E. Smith had an excellent line on so called ‘field lines’:
“Well the problem is that magnetic field lines (or electric field lines) have no real existence; they are simply a product of a mathematical representation of the Vector forces that act on magnetically susceptible materials. The action of the iron filings in the high school experiment, is as was suggested, that each filing acts as a miniature bar that can physically align itself to the lowest local energy state in the force field that surrounds the “magnet” or charged body, in the case of electric fields. It is important to remember that the field lines are a purely fictional creation of our imagination; just as isobars, and isotherms, are fictional representations of weather data.
But what is important to remember about magnetic and electric fields, is that these are vector quantities, which have, a point of action, magnitude, direction, and sense of direction; like all vector quantities. The second important point is that electric and magnetic fields are single valued functions. Since fields from multiple sources simply add vectorially, all four attributes of the resultant vector are single valued; they cannot have two different values at any point in the field, at the same time.
It’s an elementary deduction from that simple fact, that field lines cannot cross; since that must imply two different directions for the vector at a single point. And we know that is physically impossible, since points themselves exist nowhere in the real universe (nor do ANY of the other trappings of mathematics) it is all fictional stuff that we made up out of whole cloth to describe (often exactly) the behavior of our models of reality, which also are a complete fiction.
The real universe is far to complex and chaotic for us to ever explain; and the best we can do is concoct fictitious models that appear (with our current state of knowledge) to emulate what we observe the real universe to be doing. In that sense, our models, and the theories that describe the rules for manipulation of those models (mathematics); are merely tools that help us visualize why our real observations are what they seem to be.
That is why we can have valid multiple models of the same phenomenon; such as the dual wave/particle descriptions of electromagnetism. In Maxwell’s representation of “electromagnetic fields”, the magnetic “lines of force”, and the electric “lines of force” are always everywhere perpendicular to each other, and also perpendicular to the direction of energy flow; which would be the ray direction in classical ray optics, or the photon direction in the particle model. Something tells me that direction is the “Poynting Vector”; but I’m 50 years rusty on this stuff so I would have to defer to Phil or Leif on that.
So that cartoon above is truly a cartoon; since those apparently intersecting field lines cannot exist. the crossing point is a singularity where the vector has two different directions; which is silly.
And none of that says anything about whether “reconnection” is real or not; I have to plead complete ignorance on that one.”
For explaining science as it is, without the ‘fluff’, George E. Smith’s posts are among the best.
Wow you guys.
What is “fluffy?” Why refer to all the neighboring clouds as “fluffy?”
For the last 11,000 years approx. our solar system has been located in an interstellar cloud called the Local Cloud. This has been a warm cloud with moderate density.
The Local cloud is butt up against a cloud, (that they think) is caused by the interaction of our “Local cloud,” with the neighboring G cloud. This transition zone is called MIC (micro interstellar cloud).
G cloud is a cooler and faster and more dense cloud than has been our “local” cloud.
THEY KNOW about the transition zone called MIC (that exists between “Local” and G cloud) and that it was hot and turbulent and that shock waves were occurring. THEY KNOW the solar system is in the transition zone NOW! And very soon we will be entering the cooler, faster, denser G cloud.
Why the heck we call this “fluffy” is …..ick.
I think the thought discussions here should be more along the “lines” of coooling and dampening effects of G cloud now making its prescence known within the heliosphere.
But have at er guys, we all learn some things when you do.
There, woke up late on the wrong side of the bed and had my rant.
Bart (13:01:02) :
anna v (10:27:07) :
“…an electron, for example, is both a wave and a particle…”
Bart: No, it is a particle which moves with apparent wavelike properties in common experience, just like photons. See here.:
And I guess, Feynman: I want to emphasize that light comes in this form – particles. It is very important to know that light behaves like particles, especially for those of you who have gone to school, where you were probably told something about light behaving like waves. I’m telling you the way it does behave – like particles.
Feynman was a great physicist and a great teacher. This does not mean that he can be quoted as the Pope on physics.
QED does treat photons as particles Experiments show that both particles and light quanta have wavelike properties and particle like properties, depending on the experiment. Experiment trumps theory, though I do not believe there is a contradiction here. The statement served Feynman to describe QED, which is after all a symbolic way of integrating crossections, theory that is.
And Feynman could be wrong, as he was when he resisted with papal strength the emergent at the time QCD theory.
Gregg E. (00:39:55) :
Sound can’t travel in the vacuum of space, therefore there’s no such thing as a supersonic velocity in space.
In space plasmas [Alfven] waves can still propagate. Supersonic here simply means faster than the speed of these waves. The solar wind is 11 times supersonic, ‘Alfvenic Mach Number’ is thus 11.
Meet “fluffy?”
Local interstellar cloud 7500K+-1500K (LIC)
Micro interstellar cloud 9900K (MIC)
G cloud 5500K +-400K (G)
What kind of terrestrial effects would we have seen while the heliosphere was moving through a 9900K slim and slender MIC cloud. (don’t answer that.)
What kind of terrestrial effects would we begin to realize when the heliosphere enters 5500K cloud? (don’t answer that)
rant over
Carla (05:51:44) :
THEY KNOW about the transition zone called MIC (that exists between “Local” and G cloud) and that it was hot and turbulent and that shock waves were occurring. THEY KNOW the solar system is in the transition zone NOW! And very soon we will be entering the cooler, faster, denser G cloud.
Hey Carla. Who are ‘THEY’ and what is your source of information about what ‘THEY’ know?
Anna – it is not a contradiction to say that particles can move as waves. Have you ever driven the freeways in a large city at rush hour? Your car can undoubtedly be described at some scale as a “particle”. How does it move?
Radun (03:17:19) :
“But what is important to remember about magnetic and electric fields, is that these are vector quantities…”
Actually, the electric and magnetic fields are manifestations of a rank 2 tensor.
“In Maxwell’s representation of “electromagnetic fields”, the magnetic “lines of force”, and the electric “lines of force” are always everywhere perpendicular to each other…”
Only in a radiating field in lossless media.
“So that cartoon above is truly a cartoon; since those apparently intersecting field lines cannot exist. the crossing point is a singularity where the vector has two different directions; which is silly.”
There is no singularity, there is superposition. They add vectorially.