Astronomy Without A Telescope – Cosmic Magnetic Fields

Article Updated: 24 Dec , 2015


The mention of cosmic-scale magnetic fields is still likely to met with an uncomfortable silence in some astronomical circles – and after a bit of foot-shuffling and throat-clearing, the discussion will be moved on to safer topics. But look, they’re out there. They probably do play a role in galaxy evolution, if not galaxy formation – and are certainly a feature of the interstellar medium and the intergalactic medium.

It is expected that the next generation of radio telescopes, such as LOFAR (Low Frequency Array) and the SKA (Square Kilometre Array), will make it possible to map these fields in unprecedented detail – so even if it turns out that cosmic magnetic fields only play a trivial role in large-scale cosmology – it’s at least worth having a look.

At the stellar level, magnetic fields play a key role in star formation, by enabling a protostar to unload angular momentum. Essentially, the protostar’s spin is slowed by magnetic drag against the surrounding accretion disk – which allows the protostar to keep drawing in more mass without spinning itself apart.

At the galactic level, accretion disks around stellar-sized black holes create jets that inject hot ionised material into the interstellar medium – while central supermassive black holes may create jets that inject such material into the intergalactic medium.

Within galaxies, ‘seed’ magnetic fields may arise from the turbulent flow of ionised material, perhaps further stirred up by supernova explosions. In disk galaxies, such seed fields may then be further amplified by a dynamo effect arising from being drawn into the rotational flow of the whole galaxy. Such galactic scale magnetic fields are often seen forming spiral patterns across a disk galaxy, as well as showing some vertical structure within a galactic halo.

It is anticipated that next generation radio telescopes like the Square Kilometre Array will significantly enhance cosmic magnetic field research. Credit Swinburne AP.

Similar seed fields may arise in the intergalactic medium – or at least the intracluster medium. It’s not clear whether the great voids between galactic clusters would contain a sufficient density of charged particles to generate significant magnetic fields.

Seed fields in the intracluster medium might be amplified by a degree of turbulent flow driven by supermassive black hole jets but, in the absence of more data, we might assume that such fields maybe more diffuse and disorganised that those seen within galaxies.

The strength of intracluster magnetic fields averages around 3 x 10-6 gauss (G), which isn’t a lot. The Earth’s magnetic fields averages around 0.5 G and a refrigerator magnet is about 50 G. Nonetheless, these intracluster fields offer the opportunity to trace back past interactions between galaxies or clusters (e.g. collisions or mergers) – and perhaps to determine what role magnetic fields played in the early universe, particularly with respect to the formation of the first stars and galaxies.

Magnetic fields can be indirectly identified through a variety of phenomena:
• Optical light is partly polarised by the presence of dust grains which are drawn into a particular orientation by a magnetic field and then only let through light in a certain plane.
• At a larger scale, Faraday rotation comes into play, where the plane of already polarised light is rotated in the presence of a magnetic field.
• There’s also Zeeman splitting, where spectral lines – which normally identify the presence of elements such as hydrogen – may become split in light that has passed through a magnetic field.

Wide angle or all-sky surveys of synchrotron radiation sources (e.g. pulsars and blazars) allow measurement of a grid of data points, which may undergo Faraday rotation as a result of magnetic fields at the intergalactic or intracluster scale. It is anticipated the high resolution offered by the SKA will enable observations of magnetic fields in the early universe back to a redshift of about z =5, which gives you a view of the universe as it was about 12 billion years ago.

Further reading: Beck, R. Cosmic Magnetic Fields: Observations and Prospects.

80 Responses

    • The heliosphere extends more like 100 AU (in radius).

      “…voyager will soon be toast.” There are two of them and I don’t think there are strong reasons to believe they will be toast – although they will run out of power in around 10 years.

      It’s Mr Fraser Cain.

      I have only deleted abusive comments – which I have done once in my 2 years with Universe Today (we have nice commentors). A senior editor may choose to delete your comment – it does fit the ‘pet theory’ category. Also, I don’t see any connection between it and the content of the article.

    • Dominion says:

      wow. really? i’ve read this a few times and still can’t quite make out what you are trying to say. i have no problem reading your opinions about your pet theory. i usually find them interesting and amusing. it would really help your credibility if you could present your ideas in a coherent manner. ranting the way you do just sort of makes you sound crazy. how about some citations? give some links so that we can confirm what you say. who is this nobel prize winner that thinks gravity is a psuedo-force?
      i wouldn’t worry about Crumb. your post is beneath him. as much fun as it would be to read him squashing you, i rather hope he ignores you and instead delivers the quality science we so enjoy here.

      • Torbjorn Larsson OM says:

        Well, “my scientific opinion and belief” _is_ amusing, since you can’t have both value grounds (judgment on science and belief on nature) without inviting conflict.

        In this case “scientific opinion” is clearly a misnomer since nothing in the comment invites us to believe an actual understanding of science so even less study of same. “Opinion on science”, which if uninformed is tantamount to “belief” is more like it.

        And of course “belief on science and belief on nature” is not inviting conflict at all. It is also not very interesting on a science blog – the “no pet theory clause” is very wise. Questions would be interesting, whether uninformed or informed.

        And that is _my_ opinion on nature of things. (¬_¬)

    • Andrew James says:

      I just read the comments UT article; Satellite Captures 3-D View of Violent Storms that Ravaged the US on April 27-28

      What you call others there isn’t insults too?

      I think you are clearly a hypocrite.

    • I am not sure how accurate this information is. It rather looks like contour lines on a map,but I am dealing with galactic geography here and there are rules.
      Allowing for a 31 million light year distance, what is the rotatonal speed of M51.?
      Assuming that the picture with spin speed represents the position on 1 May 2011 ,this is a double barred spiral Galaxy using light as a shield. It is a system Galaxy so this local Galaxy must be in system or M51 will refuse to release any information other than the pretty pictures.
      Outer Spiral arms are checked on a STYLE matter.
      I am not sure the local physicists are up to speed with Galactic Geography.
      However this picture is at least an attempt at Galactic Geography.
      First a red picture of M 31 now this.I suppose an improvement. Let me say Double Barred spiral but Triple? Needs to be a triple. I am not sure thay want to speak to M51. More importantly,what is the view in M51?

  1. I’m sorry about ranting from past wounds, and appreciate Dominion’s and Nerlick’s kind yet strong constructive criticisms. Gentleness is strength and strength is gentleness. Nobel prizer Richard Feynmann, famous for Feynmann diagrams, said Gravity is likely a pseudo force in “Lectures on Physics, chap 12-11. Coulomb’s Law is Newton’s Gravitation equation, by substituting masses for charges, and using a different universal constant. The electrical and gravitational force, between charges or mass, is proportional to the product of the charges (masses) / square of the distances apart. Einstein’s field theory asserted that electricity and gravity have an interrelated relationship, and can be expressed by common equations. Einstein used a charged sphere and isolated charged points in space, to develop his theory of relativity, which is Electro-Gravity. Both Magnetic and Electric fields exist simultaneously. If you ride with the solar wind, their is not an electric field present. The heliosphere is a huge current sheath, and I think it is electro-gravitational in nature.

    • Torbjorn Larsson OM says:

      Gravity is likely a pseudo force

      I don’t know the context (it’s a long standing item on my reading list), but for the record: gravity is a pseudo-force in the effective theory of general relativity. I.e. apparent acceleration of mass is caused by spacetime curvature.

      But that doesn’t mean that it isn’t a bona fide force. Already Newton’s theory of gravity tells us this. And general relativity tells us this.

      What “pseudo-force” designates is that it is an apparent force that comes from the observer inhabiting a non-inertial frame of reference. Apparent forces are a class of forces, no less real than others. Ask the observers!

  2. Lawrence B. Crowell says:

    The charge to mass ratio for an electron is e/m = 1.76×10^{11}C/kg and for a proton 9.58×10^7C/kg. The Lorentz force is F = evxB (cross product} and F = ma. So compute the acceleration for interstellar charged particles travelling around 10^5m/s for a 10^{-6} gauss (10^{-10}T) field and you get about 10 m/sec^2. That is not a whole lot. It is about the acceleration of Earth’s gravity. So charged particles are going to travel in large arcs or circles. It is not hard to calculate the size of these arcs.


  3. Ivar Nielsen says:

    {Violation of comment policy: text deleted.}

    • Andrew James says:

      No, you are incorrect in nearly everything what you say here. If you had the mathematical ability, you could just possibly have an useful argument. All I see is someone just riding on the back of others untested and unqualified ideas, which you cannot even reference.

      All you say above is really open supposition where the observational evidence does not match with your heretical theories. If you want to follow such unsupported theories, you be best to make sure of your own facts before denouncing the accept theory or the observations that support it.

      Idea. Read David Crawford’s on-line book Curvature Cosmology (linked). [His cosmology papers have been mostly rejected by peer review and paper referees; mostly as it fails even the most basic of the observational evidence test.]

      Only one statement will easily do you in here…

      You say “The CMB has always been and cannot be accounted as an evidence of Big Bang.

      Even the most radical of cosmological theories. (I.e. Crawford above), says it quite well;
      Cosmic microwave background radiation (CMBR) was one of the most significant discoveries in cosmology in the 20th century. It has a black body spectrum to a high accuracy with a temperature of 2.725±0.002 K (Mather et al., 1999)… These observations are so precise and so well verified that it is essential that any cosmological model should be able to explain them. ”

      Yet clearly you don’t explain the CMB, you just ignore it completely.

      Oh. Much of what you say has little to do with comic magnetic field as elude to by Steve in this article. Do you have a useful comment on this particular story in mind?

      • Andrew James says:

        Oh. Crawford makes another interesting point about the CMB and the four models he examines. He interestingly says; “The main dependence is due to the differences in the electron density. Another important factor is the assumption that the universe has uniform density when it is apparent that it has large density variations.

        Yes, how about the electron density? Umm. After reading this interesting article, how homogeneous is the electron density throughout the universe?

        Nearly everything you have said above plainly ignores that single fact. Perhaps you should considered the evidence of the electron density throughout the universe before going off half-cocked with ideas to supplant or dismissing some standard cosmology?

        So tell us all about this grand universal electron density, please?

      • Jon Hanford says:

        “Read David Crawford’s on-line book “[Curvature Cosmology]“ (linked). [His cosmology papers have been mostly rejected by peer review and paper referees; mostly as it fails even the most basic of the observational evidence test.]”

        I’ve seen a couple of papers by Crawford posted at arXiv, but I wasn’t aware he had a book on the subject. And yes, I see nothing to his notions either.

        Btw AJ, you’re link to the book leads back to this article. Is this it?

      • Torbjorn Larsson OM says:

        “The CMB has always been and cannot be accounted as an evidence of Big Bang.”

        Not only does it test Big Bang expansion, IIRC it constrains influence of magnetic fields (or at least electron density, I see) _and_ inflation. Planck will hopefully use it to test inflation on its lonesome.

        And Planck will constrain inflation models (which WMAP started, I think) that can take us not only before “Big Bang” expansion but before inflation expansion and possibly further. CMB is awesome!

    • Uncle Fred says:

      I thought we deleted unsupported personal theories here?

    • {Violation of comment policy: text deleted.}

  4. Andrew James says:

    Thanks for the interesting story. It is surprising that we know little about the spaces between galaxies or in the dark depths between them. I was intrigued with this article from the first place as it gives a nice balance of the actual physics that so often hotly and wildly debated here.
    I think it is the sensitivity of the polarisation measures that is going to be the next revolution here — observation instead of mere theory. As said in the linked article;
    Polarized emission at optical, infrared, submillimeter and radio wavelengths holds the clue to measure magnetic fields in galaxies. Optical linear polarization is a result of extinction by elongated dust grains in the line of sight which are aligned in the interstellar magnetic field… However, light can also be polarized by scattering, a process unrelated to magnetic fields and hence a contamination that is difficult to subtract from the diffuse polarized emission from galaxies, e.g. M51 (as in this article’s image)”
    I was also taken by the overall picture that;
    Linearly polarized synchrotron emission emerges from ordered fields in the sky plane. As polarization “vectors” are ambiguous by 180 [degrees], they cannot distinguish regular (coherent) fields, defined to have a constant direction within the telescope beam, from anisotropic fields, which are generated from turbulent fields by compressing or shearing gas flows and frequently reverse their direction within the telescope beam. Unpolarized synchrotron emission indicates turbulent (random) fields which have random directions in 3-D and have been amplified and tangled by turbulent gas flows.

    This, though perhaps not as eloquent written, does mirror what often has been stated previous given comments made within other UT stories. It is a general picture of ordered and disordered magnetic fields, and it seems in the near future, we may have a better concept of where it fits in the scheme of things. Rightly, this article concludes;
    Detection of a general IGM field, or placing stringent upper limits on it, will provide powerful observational constraints on the origin of cosmic magnetism.

    I think this is sensible science driven by reality of the situation (without all the hysteria).

    As another comment, Zeeman splitting is probably only visible in the bright stars in their observed spectra (Stark effect, from an electric field, only is very rare cases.) I am quite surprised the radio spectral lines can or possibly could do the same.

    Thanks Steve for this article.

    It should, for once, nearly satisfy all comers!
    (Apologies for the length of this reply.)

    • Thanks Andrew – yes I saw the M51 comment. The image is just magnetic field data (noise included) – not necessarily a magnetic field map.

    • Andrew James says:

      Oh. As for the article saying on IGM fields;
      The goal is to detect an IGM magnetic field of 0.1 nG,…
      Frankly, that isn’t an awful lot to play with! (Now that is sensitive.)


      {Violation of comment policy: text deleted.}

  5. Richard Kirk says:

    “I was intrigued with this article from the first place as it gives a nice balance of the actual physics that so often hotly and wildly debated here.”

    I think there is very little debate about the actual physics here. If it looked like scientific debate to you, I hope the following may help…

    A magnetic field will cause a moving charged particle to move in a circle. If the particle has a small charge or a large mass or is moving fast (and I am not talking about relativistic speeds here) then the particle will move in a large circle. If the magnetic field is weak in interstellar space then even something like an electron, which has the smallest mass per unit charge, will move in a very large circle. But that’s okay, because space is pretty large too. This could shape the flows of charged particles between the stars. That is what the article is talking about.

    Could such forces shape the galaxies themselves? It is very hard to see how. Most bulk matter such as planets and stars is not charged. If you have a bar magnet, then the strength of the field drops off as the cube of the distance, not the square as gravity does. You can see the power of magnetic fields when they chuck streamers out of the sun against gravity. However, the auroras at the earth are the effects of the charged particles flung out by the sun, and not a direct effect of the solar magnetic fields. By the time you have gone to intergalactic distances, magnetic field strength has gone down to tiny levels. We can measure the total magnetic field along a line of sight by measuring polarization using radio telescopes. We don’t always know where along the line of sight the magnetic field lies, but if you look at the map of the Whirlpool Galaxy in the article, then the map seems to fit the visible features, so we guess that is where the magnetic field lies. If we assume that most of the total magnetic field lay in the Whirlpool Galaxy itself, then we can get a figure of the field strength. That field is about 0.000008 time the earth’s magnetic field: not zero but not much either. If stars are not charged but have a magnetic field, then it is our theory – and a pretty reasonable one it is too – that the stars shape the magnetic field, and not the other way around.

    Unfortunately, when any article mentions magnetic fields, we get these strange posts saying that its the magnetic field that is pulling the stars into spirals. No proof; no evidence; just the assertion, and the rubbishing of anything that disagrees with the belief. You can see that Steve, the author of the article, was cringing in anticipation of the replies he knew were coming.

    Speak your truth quietly and clearly, and listen to others, even the dull and ignorant; they too have their story. Okay, we’ve done that today. Tick. I just wish they would vary their story a bit.

    • Well, I don’t know about cringing 😉

      • Richard Kirk says:

        Apologies to Steve. ‘Cringe’ means the same as ‘wince’ to me (UK): ‘oh no, I know what’s coming next, and it won’t be nice’, but posting it anyway. I have looked up the definition on the web and I get “bend one’s head and body in fear or in a servile manner” which isn’t what I had meant at all. Oh dear, my bad. Mmm, crow, nom nom.

    • Andrew James says:

      Nicely said.
      However, when I made the statement; “I was intrigued with this article from the first place as it gives a nice balance of the actual physics that so often hotly and wildly debated here.”, it was actually an invitation for those deviating from the mainstream to redress some of the quite incorrect claims used by followers of plasma physics.
      The “article” in which I am referring is Beck’s, and the physics which it discusses.
      At least this story overall gives a perfect opportunity to discuss how much or how little magnetic and electric field dominate the universal scale of the universe. Its point is

    • Andrew James says:

      Its whole point is gaining new observational evidence in the future to be able to support theory or invent new ones. We can only support what we observe. We cannot fully support some wild ideas because it applies in one circumstance and therefore it must applied carte-blanch in another. (It isn’t science if it does.)
      Also the proponents of the so-called “electric universe” (especially the IEEE) often bitterly complain that scientific funding does not support observational resources for their overall tenets of what they profess drives the universe. Here is an excellent example of the contrary view.
      Magnetic and electric fields do play a role in astronomical phenomena. What we don’t know is how much and to what extent. Maybe we will find out, but this time have the observations to back it up those ideas.

      • Torbjorn Larsson OM says:

        Is IEEE in on that? Ouch.

        And they supported the “microfossils” in meteorite hypotheses of Hoover until he could push it into Wickramasinghe’s publications. Double ouch.

        “- The pseudo-science force is strong in this one.” *

        * To be fair, “microfossils” isn’t pseudoscience in paleontology but an unfortunate and unsubstantiated pattern search regime of early life work. [Schopf et al.; for a contrasting testable regime, see Brazier et al.]

        It is just that the suggestion that paleontology applies that is extra-ordinary, but without the needed extra-ordinary support.

      • Andrew James says:

        Institute of Electrical and Electronics Engineers (IEEE) does, and it is not the only organisation. Also see An Open Letter to the Scientific Community; who have made such statements as;
        To redress this, we urge those agencies that fund work in cosmology to set aside a significant fraction of their funding for investigations into alternative theories and observational contradictions of the big bang. To avoid bias, the peer review committee that allocates such funds could be composed of astronomers and physicists from outside the field of cosmology.
        Allocating funding to investigations into the big bang’s validity, and its alternatives, would allow the scientific process to determine our most accurate model of the history of the universe.
        ” Triple ouch! 🙂

      • Torbjorn Larsson OM says:

        Arp I can believe.

        As for the science process statements, it is the same idea that one could use bayesian weighting on all parameters from all theories and get something sensible out of it. We reject failed theories for a reason. Likewise we don’t avoid informed bias!

        Luckily it was published in New Scientist, and 2004: the standard cosmology proved itself around that time. I like the “Independent researchers” funny touch, even if it could be after publishing.

        Slight reediting:

        “Electromagnetism today relies on a growing number of hypothetical entities, things that we have never observed– the field, the electron and the potential are the most prominent examples.”

        How far would they get with that without being laughed out of the pages?

      • davesmith_au says:

        A point needs to be made here. The IEEE does not support Electric Universe theory, per se. They have a professional peer-reviewed journal which happens to have published a number of papers by authors who are proponents of electric universe theory. It’s not the same thing. That a peer-reviewed journal publishes something is not an indication of support of an entire paradigm. It is an indication that the reviewers considered the science therein to be sound. The IEEE publishes thousands of papers which most readers of this site would likely not even begin to comprehend. That they understand plasma better than most should come as no surprise, and is no reason to attempt to denigrate the entire organization.

      • Andrew James says:

        Wikipedia says; “While plasma cosmology has never had the support of most astronomers or physicists, a few researchers have continued to promote and develop the approach, and publish in the special issues of the IEEE Transactions on Plasma Science that are co-edited by plasma cosmology proponent Anthony Peratt.”

        I believe I have even seen you even writing about aspects of these “special issues”, and they often appear in such stories of alternative cosmologies. (Sometimes these are even quoted as peer reviewed, even though they are not really astrophysical papers.)

    • Ivar Nielsen says:

      Quote: “If stars are not charged but have a magnetic field, then it is our theory – and a pretty reasonable one it is too – that the stars shape the magnetic field, and not the other way around”, unquote.

      When we have a electric charge, we also have a magnetic field – and visa versa. It is not about one way or another but about both ways. So both possibilities are in play.

  6. Aqua says:

    “The strength of intracluster magnetic fields averages around 3 x 10-6 gauss (G), which isn’t a lot.” The IMF may be weak but what is key here is not the strength of the field instead, it’s the size! Think in terms of a giga parsec fulcrum. At that scale, a breeze could move a galaxy!

    • I don’t think this is correct. The difference between a hurricane and a breeze is energy density, not volume (or size). It’s all the same atmosphere 🙂

      It is reasonable to assume that as the universe continues to expand these intracluster magnetic fields will continue to get weaker – and 3 x 10-6 gauss (G) really isn’t a lot. The scientific interest here is mainly around what these fields can tell us about the past history of the universe.

    • I like it. Moving Galaxies. A bit like moving plates! Fancy stylised plates. Small plates placed on a stick! Single ,double and Triple Barred spiral. Hidden, black and gold! Shall I talk Balsa, Au and Ag. Blue white! Heavy white!Standard style. Insited upon, but not forced.

  7. Lawrence B. Crowell says:

    The map measures the power of EM radiation, watts per meter^2, from M51. This radiation is largely due to Bremsstrahlung radiation. Charged particles move on helical paths in these magnetic fields. The centripetal acceleration induces the emission of radiation by the Abraham-Lorentz equation.

    The Zeeman effect is due to the projection of the magnetic moment of an atom with a magnetic field. This gives a Hamiltonian H = -m*B. the magnetic moment is m = m_bgL/hbar, for m_b the Bohr magneton g =~ 2 the Lande g-factor, L the angular momentum and hbar the Planck unit of action. The angular momentum is some unit of hbar, L = N*hbar and the Bohr magneton is m_b = e*hbar/2m, and is equal to about 10^{-24}J-T^{-1} or ~ 10^{-5}ev-T^{-1}, here the unit T is a unit of Tesla. The Hamiltonian acts on states to give an energy and this energy per atom for a weak galactic magnetic field is about 10^{-34}J or ~ 10^{-14}ev. This is extremely small. The periodicity of an atom is about one second or a frequency of about 1 Hz. This is very low frequency radiation. So the expected average power output from an atom might be around 10^{-34}J/sec = 10^{-34}watts.

    However, for a mole of such atoms, 6.02×10^{23} this amounts to about 10^{-10}J/mole. A star consists of about 10^{30}kg or 10^{33}moles, and an estimate of the amount of energy released by a galactic mass of gas would then be around 10^{43}moles. This means the estimated power output by the Zeeman effect by atoms in a galaxy is around 10^{32}watts. This is the radio power output equivalent to the luminous power output of about a million solar class (G-class) stars. Not bad! So this is a substantial part of the radio spectrum power output. I would need to do some calculation estimates of the Bremsstrahlung power output to make a comparison with that. However, time is not exactly permitting at the moment.

    Stark splitting is related to Zeeman splitting, but it is due to the dipole interaction between the dipole moment of an atom and the electric field. This is a significantly different.


    • Torbjorn Larsson OM says:

      In the face of this tour de order of magnitudes and the low permittivity of time, I’m going to be extremely “questionable”/nitpicky:

      – The Zeeman effect splits transitions of emission lines, the inverse Zeeman effect splits absorption lines.

      Most of those would be visible (stars) or IR (molecules). Of the former I assume the bulk light would be scattered to a thermal spectra.

      So I don’t get this, unfortunately, too little data. You are estimating what looks to be the Zeeman energy that relates to the energy of the splits, not the emission as such?

      – Units of Tesla may exist, but the one that bears his name didn’t originate with him. It is “a tesla” (T).

      • Lawrence B. Crowell says:

        The energy calculation is about correct. The emission rate, which I approximate with the periodicity of the radiation, is probably an gross over estimation. This power estimate is about the maximum which could likely occur. I would not be surprised if the power of this radiation is an order of magnitude lower. This is basically a “back of the envelope calculation.”


      • Torbjorn Larsson OM says:

        I still don’t get it. The energy should go into the splitting energy differences, not the actual transitions.

        I must be tired because I don’t see the connection between these disparate phenomena. Are you arguing that the Zeeman effect is frustrated and instead goes into radio emission? It’s a mystery, it is.

      • Torbjorn Larsson OM says:

        Or maybe you mean _not: “the estimated power output by the Zeeman effect” but “the power output [of radio emission] estimated by the Zeeman effect”.

        That would make sense, finally.

      • Lawrence B. Crowell says:

        The radio power is not due to energy induced by the Zeeman effect, but it provides the splitting of atomic levels so the emissions can occur. As a result the second is probably more accurate.

        There is a lot of phenomenology involved here that I can’t make a quick judgment on. The basic physics though is not hard to understand. If you have a lower atomic level A and an upper level B, the energy difference is E(B) – E(A). Any photon with energy greater than this can be absorbed by an electron in the A level, causing the electron to shift to the B level and the photon to scatter off with energy reduced by E(B) – E(A). Now suppose there is a magnetic field which splits the B level into B + b and B – b. This means that there will be transitions from B + b to B – b with the emission of a low energy photon. This may in fact be a preferred transition if the transition from B + b is quadrupolar, but from B – b is dipolar, or if B + b directly to A is forbidden by spin. This stuff gets pretty involved and constitutes the major part of a 2nd semester graduate quantum mechanics course.

        The rate at which these transitions occur is beyond my bailiwick, where the more atomic states split by the Zeeman effect are excited the more Zeeman transitions you will observe. That part of the physics or astrophysics I am not that familiar with. So the collective power output is determined by the power input by optical and higher energy photons.


      • Andrew James says:

        I somehow missed your little discussion.
        Just to clarify the astronomical side of things….
        The Zeeman Effect is when strong magnetic fields are placed near to where the emission spectra is produced. (If it is an adsorption spectra it is called the Inverse Zeeman Effect (which most astronomers simply ignore the term) It was first found in 1896 by Pieter Zeeman. Mostly they are seen associated with sunspots or starspots, where the spectral lines often just split into two separate lines. A mean position of the two divided lines corresponds to the normal wavelength of that spectral line. Simply. The major reason that the lines split is due to the polarisation and the directions of the magnetic field as observed from the Earth. Hence, the appearance of the effect is highly dependant on the direction from which the source is viewed as relative to the lines of force.
        First time these lines were discovered photographically on the Sun during 1919 by G.E. Hale, the Zeeman effect is one quite notable part of the whole solar spectrum. Sunspots are always accompanied by powerful magnetic fields and measure from several hundred gauss to more than 3000 gauss. Earth’s magnetic field in comparison is less than one gauss.
        This effect can be seen in other stars, especially in the A-type spectral class stars. This effect in has also be seen in several stellar photospheres of the metal Chromium at 461.3 & 462.6nm. The highest field strength so far observed in an astronomical object is 4700 gauss field.

        Stark Effect

        If a spectral line is subjected to a strong electrical field, the spectral line can also split into multiple lines, that spread out like a fan. The observed effect is dependant on the direction in which the spectra is viewed between the electric field and the observer. Its effect is due to the shifting of the energy orbital levels in the atom which have the same energy as the zero field.

        These lines are rarely observed and are mostly associated with the sun, especially stellar flares, and bright hot B or A spectral type stars. Mostly they appear as a broadening of the Balmer lines or with Helium at 417.0 and 381.9 nm.

        The physics of the line creation is exactly as LBC has already described.


      • Lawrence B. Crowell says:

        The quantum physics for the Zeeman effect is not difficult to understand, as I outline it in this thread on May 1, 2011 at 12:48 pm. I give an estimate of the power output a galaxy might produce by atomic level splitting by the galactic magnetic field. I assumed that atomic states were refreshed at the periodicity of this radiation. That is some sort of upper bound. What is unknown to me is the energy available to atoms in a galaxy, mostly as interstellar gas, which would produce the long wavelength EM radio fields.


      • Andrew James says:

        Opps!! They will jump on me if….
        The highest field strength so far observed for the Zeeman effect in a average main sequence star is 4700 gauss field. (except our Sun)

  8. Andrew, You said it yourself to story author Steve…This story is a “nice balance of actual physics often hotly debated here, and was actually an invitation for followers of plasma physics.” You also said “what we don’t know is how much and to what extent, and we require observations for new theories.” There is new evidence from Herscel by two scientists, Dr Andre and Pilbratt, who have actually seen stars forming like beads on strings in and along dense cosmic filaments, in IC 5146, Aquila, and Polaris. Over 60 observed cosmic filaments there all have the same widths ~0.3 light years across. Cosmic filaments are confined by magnetic fields and are millions of degrees kelvin. Shockwaves of sonic booms are believed to form these filaments they say. As for the weakness of the galactic magnetic field strengths, it is the size that matters most. It might only take a shockwave or wind breeze from supernovas to move galaxies along magnetically confined filaments, as Aqua suggested.

  9. Andrew James says:

    Just to let you all know. According to the Thunderbolts Forum, Mr Hologram (Pat) here in now claiming of this particular new thread; “Magnetic Fields and Electro-Gravity at UniverseToday by quantauniverse Sun May 01, 2011 6:15 am

    “A heated discussion is underway over Cosmic Magnetic Fields, and the role of Electro-Gravitational forces. See the story, at [this thread.]
    Please leave comments, because the “Gravity scientists” there are now politely willing to allow Electric Universe believers and members to post their views and present their scientific facts and evidence. The story admits that they often wish to move away from these highly debatable topics. ”

    Eh? No one has said anything like this at all.
    I’m sorry, but isn’t this really just totally misrepresenting the facts?
    It seems all pretty desperate act just to support your own confused arguments.

    Really bizarre behaviour, I’d think.

  10. Split_Infinity says:

    Can someone explain to me why this article may be controversial?

  11. IVAN3MAN_AT_LARGE says:

    Gordon Bennett! Whenever the keywords “magnetic fields” or “electric currents” appear in the subject title on Universe Today, the “Electric Universe” nutters descend onto the comments section like goddamn wasps on a Sunday summer picnic.

  12. @Split_Infinity,

    “Can someone explain to me why this article may be controversial?”

    In the 1970 after the Big Bang (BB) became the dominant model of cosmology, this BB model was challenged on many levels by Hannes Alfvén, a Swedish Electrical Engineer and research scientist, and Nobel laureate in plasma physics. Alfvén developed his own cosmological model where electrical currents in the form of linear currents of stellar type plasma (protons and electrons), along with their related magnetic influences, were primarily influential concerning the initial creation and form of galaxies within an infinite universe. This was not considered by most to be a mainstream model and there were many critics at the time that asserted that electro-magnetic influences and related mechanics was incompatible with the Big Bang model.

    Alfvén’s cosmological model also relied on matter-antimatter interactions to explain the expansion of the universe while critics pointed out that there was no evidence for galactic electrical currents, its related magnetism, or substantial matter-antimatter interactions in galactic cores.

    This cosmology still has some followers today but very few mainstream physicists and generally none are outside the plasma physics arena. This theory is called Plasma Cosmology and is also called by its detractors as the Electric Universe model because its followers equate high-speed plasma currents with electrical currents and its related magnetic influences.

    Although we have come to know of more a more magnetic influences within galaxies as Alven had proposed, most believe it is not enough to influence galaxy formation as Alven proposed and there has been little or no evidence since his proposal to support his visions of great volumes of anti-matter withing the universe.

    quote from the article above:

    “The mention of cosmic-scale magnetic fields is still likely to (be) met with an uncomfortable silence in some astronomical circles – and after a bit of foot-shuffling and throat-clearing, the discussion will be moved on to safer topics. But look, they’re out there. They probably do play a role in galaxy evolution, if not galaxy formation – and are certainly a feature of the interstellar medium and the intergalactic medium.”

    Some of Alven’s “uncomfortable” and one-time very controversial assertions are being proven to some extent by present-day evidence of galactic magnetic fields and their implication of the inside out formation of galaxies, generally in contradiction to the standard model. His ideas of anti-matter abundances that could be the cause of cosmic expansion, however, are still without evidential support making it even more unlikely today than 40 years ago when Alven first proposed the model.

    • There’s a balanced coverage of this plasma cosmology here:

      I note this has nothing to do with Beck’s paper – which is focused on observational data, not theoretical cosmologies.

      • davesmith_au says:

        I don’t know of any serious scientist who references Wikipedia. The content of Wikipedia can change from instant to instant, and that fact alone should preclude it as a serious reference for any controversial topic.

      • IVAN3MAN_AT_LARGE says:

        I don’t know of any serious scientist who references Wikipedia.

        Dr. Phil Plait does, Dr. W.T, “Tom” Bridgman does, and the APOD website does so almost daily.

        The content of Wikipedia can change from instant to instant,…

        That’s because Wikipedia is constantly evolving with new information, unlike printed encyclopedias — which are static and, in this technological age of scientific advancement, start to become out-of-date as soon as they are printed.

        …, and that fact alone should preclude it as a serious reference for any controversial topic

        That’s the same argument used by creationist nutters who take the Bible literally!

      • IVAN3MAN_AT_LARGE says:

        Erratum: That should be a dot (period), not a comma, after the “T”.

        (No bloody preview/edit facility here — Grrr!)

      • davesmith_au says:

        As I said, serious scientists, not popularist PR machines and self-styled debunkers.

      • Andrew James says:

        Is this the reason why you disagree with Wikipedia?
        While plasma cosmology has never had the support of most astronomers or physicists, a few researchers have continued to promote and develop the approach, and publish in the special issues of the IEEE Transactions on Plasma Science that are co-edited by plasma cosmology proponent Anthony Peratt.

        I believe I have even seen you even writing about aspects of these “special issues”, and they often appear in such stories of alternative cosmologies. (Sometimes these are even quoted as peer reviewed, even though they are not astrophysical papers.)

        Would you like me to quote some pertinent examples, Dave? (i do not want to embarrass you.)

  13. Andrew James says:

    Split_Infinity May 2, 2011 at 3:08 am here asked;

    Can someone explain to me why this article may be controversial?

    Actually, it isn’t. This article refers to current knowledge of intergalactic magnetic fields and future astrophysical observations to detect those fields.
    In simple terms, these fields are generally fairly weak and are mostly incoherent, meaning unlike the magnetic fields of the Sun or the Earth (coherent, because the allow charged particles to flow along predictable paths of the magnetic field lines), they have no preferential direction or organised field lines. They are important because if we understand the strength and nature of those fields, we might find further clues to their origin and evolution. They may even tell us something of the earliest times of the universe, finds such things as how galaxies or the first stars were formed.
    The ‘alleged’ controversy is that some wrongly think magnetic fields and ionised matter dominate the large-scale structures of the universe. It is, sadly, remains both unproven and remain unlikely as based on present knowledge and what we observe in many large-scale astrophysical phenomena.
    In fact, regardless of the stance of proponents or detractors, these future observational using either LOFAR (Low Frequency Array) or the SKA (Square Kilometre Array) will give us a much better perspective of the nature and strengths of these magnetic fields.
    As yet, we have little direct or factual about cosmic magnetic fields and of the environment in between galaxies and galaxy clusters. Until we do, wildly speculating on what we will or won’t discover isn’t going to help. (It seems that some here are impatient, as the discoveries for them are not coming fast enough. Most of what they say is speculation and not fact.)

    It is far more complex in many aspects, though it paints the current picture of what we know of cosmic magnetic fields. Hope that answers your question.

  14. Andrew James says:

    “I’d like to explain the controversy over the role of cosmic magnetic fields,”
    I’m absolutely have no interested in what you say. What you have just written here has so many errors and inconsistencies, I really wouldn’t know where to start. All the incoherent rantings you write makes absolutely no sense at all. Why bother.

    Please leave it at that, before you make yourself look any more foolish.
    Thank you.

  15. [email protected] says:

    {Comment deleted for too many reasons to list}

  16. What happened to all the messages that were posted here on magnetic fields? Why were they all deleted? Isn’t UniverseToday deliberating trying to hide the truth about magnetic fields in outer space? YES they are LIARS at UNiverseToday. They erase and block out all comments that do not agree with their propaganda on dark matter, black a-holes, dark-energy-fags etc. Salacious B Crumb is a old fart cocksucker who kisses the behinds and sucks the dicks of Larsson, Uncle Fred, and Ivan, so that he be allowed to insult the members here who post true science about EU and PC.

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