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Thread: EHD Model of Stellar Accretion

  1. #1

    EHD Model of Stellar Accretion

    I don't know if I have a "model" here, or just an "idea". At the very least, it's one of a series of "ideas" on the possible applicability of EHD to a wide variety of phenomena. Does that form "model"? I'll let you be the judge. Anyway, here it is...

    We're all well aware that gravity is the primary force that causes the collapse of gas clouds into stars. But it's also possible that the electric force makes a small contribution. This sounds odd, as we have every reason to suspect that interstellar gas clouds are electrically net neutral. But this does not mean that every atom in the cloud is neutral. If aggregates are present (i.e., dust particles or anything larger), they tend to be negatively charged, and surrounded by Debye sheaths of positively charged plasma. This is because at the same temperature, electrons move faster (because they are lighter), and thus more electrons than atoms impact an aggregate (such as a dust particle). Once absorbed into the electron cloud of the aggregate, the electrons are less likely to be re-emitted. Hence a slight negative charge builds up in the aggregate, to the limits of the strength of the bonding in the aggregate versus the electrostatic potential between the body and the plasma, which pulls electrons back out.

    Now consider two negatively charged bodies near each other, with their Debye sheaths overlapping. The electric field from the negative bodies radiates outward in all directions. All other factors being the same, the charge density in the positive plasma will be the same in all directions. But in the space between the two bodies, the negative electric field overlaps. As a consequence, there will be a greater density of positive plasma between the two negative bodies. The negative bodies will then be attracted to the positive plasma between them.

    This effect is what Feyman called the "like-likes-like" principle, wherein like-charged bodies appear to be attracted to each other. They are, of course, repelled by their like charges, but they are also attracted to a shared opposite charge between them, and this pulls them together (up to a point).

    As Debye sheaths are relatively small, we'd expect the effect to be relatively weak. Yet the anomalies in the gravity model are extremely small, and the electric force is extremely powerful compared to gravity. (The electric force between the proton and the electron in a hydrogen atom is 39 orders of magnitude greater than the gravitational force.) If the observations indicate that 5 times more gravity has to be present to cause the accretion that we see, this could be explained by 5 times more mass, or by 1 charged particle in every thousand-trillion-trillion-trillion.

    So by electrostatic standards, this is a near-infinitesimal amount of force. But it might still be robust enough to make a contribution to gas cloud collapse.

  2. #2
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    In the context of stellar medium water is not a major source of material, so hydrodynamics would not be significant. This idea seems similar to the Electric Universe theories.

    http://www.bautforum.com/showthread....uot-ideas-here

    I have been entertaining the idea that dark matter is the electric field from ionized clouds with the dust rotating one way and an electron cloud flowing the opposite direction. I am not sure this is significantly different from plasma physics, which is a very main stream view of stellar mechanics.

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    Planets start off as dust bunnies, as it were. I think some of mine are showing gravitation--better get to sweeping.

  4. #4
    Quote Originally Posted by utesfan100 View Post
    In the context of stellar medium water is not a major source of material, so hydrodynamics would not be significant.
    EHD, MHD, and EMHD are ambiguous terms, and they're frequently misnomers. Hydrodynamics studies the motion of incompressible fluids, but in common usage, the "HD" part of the acronym frequently refers to flows in compressible fluids (i.e., gas or plasma). So the more proper term might be fluid dynamics, not hydrodynamics. And the topic might focus more on the effects of pressure than on flows (i.e., hydrostatics instead of hydrodynamics). People have tried to coin other terms, to more accurately designate the specific blend of disciplines in their works, but the coinages didn't stick. Most of what I'm doing is "electrostatics + fluid dynamics". Gravity is also a factor, so I could call it EFDG, but that isn't a term in common usage.

    Quote Originally Posted by utesfan100 View Post
    This idea seems similar to the Electric Universe theories.
    It IS electric, but it is not consistent with Electric Universe tenets. (It isn't huge Birkeland currents with overpowering z-pinches controlling everything in the Universe.) In fact, most of the people over there disagree with me, so to do a categorical dismissal, you have to put me in a category that doesn't want me.

    Quote Originally Posted by utesfan100 View Post
    I have been entertaining the idea that dark matter is the electric field from ionized clouds with the dust rotating one way and an electron cloud flowing the opposite direction.
    It sounds like you're saying that the ionized dust and the electrons are both in the same cloud, with opposite charges counter-rotating, is that correct? If so, why don't the opposite charges recombine?

    Quote Originally Posted by utesfan100 View Post
    I am not sure this is significantly different from plasma physics, which is a very main stream view of stellar mechanics.
    It IS plasma physics, but how? A lot of people seem to think that plasma physics always equals MHD, but a lot of the MHD work being done these days is very abstract and arguably non-physical (i.e., the magnetomotive force is not identified, and if it's hydrogen plasma, B cannot be said to be "frozen in"), while to others, plasma physics is a mechanistic discipline that tolerates simplifications but has no use for abstractions. So "plasma physics" can mean a lot of different things.

    Anyway, you figure out what labels to attach to this, because I don't care.

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    Quote Originally Posted by CharlesChandler View Post
    At the very least, it's one of a series of "ideas" on the possible applicability of EHD to a wide variety of phenomena.
    EHD is only applicable to the phenomena thta it descibes, i.e. electrically charged fluids.
    Electrohydrodynamics
    Electrohydrodynamics (EHD), also known as electro-fluid-dynamics (EFD) or electrokinetics, is the study of the dynamics of electrically charged fluids.[1] It is the study of the motions of ionised particles or molecules and their interactions with electric fields and the surrounding fluid.
    You have presented no evidence that gas clouds that collapse to create stars have a net electric charge and so EHD is inapplicable.

    The proper theory to describe a gas cloud which is electrically neutral but is ionized, e.g. by radiation, is called magnetohydrodynamics.
    You can also have an cloud of actually neutral gas (no ionization) and this is described by the usual gas laws. However as the cloud collapses it heats up, ionizes and enters into the MHD area.

  6. #6
    Call it MHD if you want, but just to be clear, I'm talking primarily about electrostatics, balanced by the hydrostatic pressure of the gas. The proposed E is between the negative bodies and the positive plasma that surrounds them. Overall, we have every reason to believe that the cloud is neutral, but it's possible that charge separations within the cloud create a net inward force on the whole thing. Once the cloud starts collapsing, I guess you could say that it's no longer electrostatics, but rather, electrokinetics. But I wanted to get comments on the proposed resting force before considering the behaviors of the collapsing cloud.

    BTW, you mentioned evidence. In the interest of clarity, I should like to point out that I'm talking about 5 charged particles per thousand-trillion-trillion-trillion (i.e., 1039). Detecting near-infinitesimal charge separations is tough here on Earth, but when the dust grains are more than a couple of light years away, it's doubtful that we'll ever have reliable measurements. Hence the only thing that can be done is to look for the anomalies in the gravity model, and guess at what other force(s) might be perturbing the measurements. In other words, if you told me that there were no gravitational anomalies, I wouldn't disagree. If you tell me that the gravitational force from known matter is only 1/5 of the requirement, I say that there might be 5 charged particles per 1039 that supply the force, as electrostatic potential. If the anomaly is 10 times greater, I say 50 parts per 1039. So it's just a matter of how big the anomaly is, and what we have laying around that might sop it up.

    So what's the point? We already have heuristically-derived formulas for the critical balance between mass and temperature that define the limits of the Jeans instability. Do we need another force, other than gravity, thrown into the mix?

    The only advantage to considering the effects of the electric force is that it might be able to eat some of the slop in the Jeans instability itself. Specifically, we know that a gas cloud is more likely to collapse if there has been a supernova nearby. While it's possible that the shock wave from the supernova increased the mass and/or lowered the temperature of the gas, thereby sending the gas cloud across the threshold for the Jeans instability, it's also possible that the UV radiation from the supernova ionized the gas, thereby increasing the "like-likes-like" force.

    So I'm not saying that we can actually measure these forces, and then compare the predictions of the model to observations as a test of its accuracy. Rather, the only "observations" are anomalies in the gravity model. So you either dial up the amount of CDM you need, and/or you get what you need from the electric force. Either way, the "model" matches the "observations" perfectly! But there will never be a way of verifying the actual existence of the slop-eater(s).

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    Quote Originally Posted by Reality Check View Post
    EHD is only applicable to the phenomena thta it descibes, i.e. electrically charged fluids.
    Electrohydrodynamics


    You have presented no evidence that gas clouds that collapse to create stars have a net electric charge and so EHD is inapplicable.

    The proper theory to describe a gas cloud which is electrically neutral but is ionized, e.g. by radiation, is called magnetohydrodynamics.
    You can also have an cloud of actually neutral gas (no ionization) and this is described by the usual gas laws. However as the cloud collapses it heats up, ionizes and enters into the MHD area.
    Thank you. I was clearly talking about Magnetohydrodynamics. It wold likely be best to ignore my tangent until I can develop it into its own thread.

    Consider the Sun. It is believed to have formed from the nebula resulting from the nova of a protosun. This sun would have emitted electrons over its lifetime, making the nebula tend towards a net negative charge.

    I am skeptical that this makes a significant change to the nebular hypothesis, or improves on its known faults.

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    Consider the Sun. It is believed to have formed from the nebula resulting from the nova of a protosun. This sun would have emitted electrons over its lifetime, making the nebula tend towards a net negative charge.
    No it isn't. Nova refers to a very specific astronomical phenomenon - it does not refer to protostar ignition. The Sun formed from the collapse of a giant molecular cloud, possibly with the assistance of a supernova blast nearby.

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    Quote Originally Posted by CharlesChandler View Post
    Call it MHD if you want, but just to be clear, I'm talking primarily about electrostatics, balanced by the hydrostatic pressure of the gas...
    Actually I think these folks might agree with you (from 2011):
    http://arxiv.org/pdf/1109.4052v1.pdf
    The First Magnetic Fields
    Lawrence M. Widrow, Dongsu Ryu, Dominik R. G. Schleicher, Kandaswamy Subramanian, Christos G. Tsagas and Rudolf A. Treumann

    There are several ways to generate magnetic fields during the epoch of structure formation. At some level, all mechanisms begin with a battery, a process that treats positive and negative charges differently and thereby drives currents which in turn generate fields. A Biermann battery, for example, can (in fact must) operate during the formation of a proto-galaxy. While angular momentum in proto-galaxies is generated by the tidal torques due to nearby systems, vorticity arises from gasdynamical processes. The same processes also drive currents and hence generate fields, albeit of small amplitude.

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    Quote Originally Posted by Shaula View Post
    No it isn't. Nova refers to a very specific astronomical phenomenon - it does not refer to protostar ignition. The Sun formed from the collapse of a giant molecular cloud, possibly with the assistance of a supernova blast nearby.
    Sorry for my ignorance. My understanding was that the giant molecular cloud was the remnants of a nova, as demonstrated by the abundance of metals in our solar system.

  11. #11
    I should also mention that the "like-likes-like" principle might be more than just a discrete secondary mechanism for gas cloud collapse -- it's possible that there is interplay between the electric force and the factors identified by Jeans. Gravity attracts; hydrostatic pressure (a function of temperature) repels; and the "like-likes-like" principle attracts. Yet it's also true that E reduces the degrees of freedom of charged particles, thereby reducing the temperature. Hence the UV radiation from a supernova that ionizes a dust cloud instantiates the "like-likes-like" principle, which is an attractive force, but it also reduces the temperature, and likewise the hydrostatic pressure. More attraction and less repulsion equals faster accretion.

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    Quote Originally Posted by CharlesChandler View Post
    Call it MHD if you want, but just to be clear, I'm talking primarily about electrostatics, balanced by the hydrostatic pressure of the gas.
    I do not "call it" MHD. MHD is the theory that you need to use to model a cloud of plasma. If you do not have a cloud of plasma then all you need is classical gas laws.

    Charge separation is impossible for a cloud of neutral atoms.
    Charge separation is possible and well known for a cloud of ionized atoms. This is not about electrostatics. This sounds like double layers which are of order of some tens of the Debye lengths. The Debye length for the ISM is ~10 metres and gets smaller for denser plasma, e.g. 0.001 metres for the ionosphere.
    Your "electrostatics" cannot balance the hydrostatic pressure of the gas as far as I can see.

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    Quote Originally Posted by quotation View Post
    Actually I think these folks might agree with you (from 2011):
    http://arxiv.org/pdf/1109.4052v1.pdf
    The First Magnetic Fields
    Lawrence M. Widrow, Dongsu Ryu, Dominik R. G. Schleicher, Kandaswamy Subramanian, Christos G. Tsagas and Rudolf A. Treumann
    No, I don't think so, the Widrow et al. paper describes electrodynamics, as there is no way to generate magnetic fields through "electrostatics balanced by hydrostatics." I have no idea what you think to claim with the quote, but that is everything but what CC is talking about, albeit that he seems to have trouble naming his process EHD or MHD. However, in the OP there is no mention whatsoever about magnetic fields. CC wants to let dust somehow coagulate through charge in a "like attracts like" (I have to look up what Feynmann really says about that process). Now you come up with the discussed Biermann battery, which is a way of generating weak mangetic fields through the creation of vorticity:

    Quote Originally Posted by Widrow et al.
    In the hierarchical clustering scenario, proto-galaxies acquire angular momentum from tidal torques produced by neighboring systems (Hoyle 1949; Peebles 1969;White 1984). However, these purely gravitational forces cannot generate vorticity (the gravitational force can be written as the gradient of a potential whose curl is identially zero) and therefore the existence of vorticity must arise from gasdynamical processes such as those that occur in shocks. More specifically, vorticity is generated whenever one has crossed pressure and density gradients. In an ionized plasma, this situation drives currents which, in turn, generate magnetic field. This mechanism, known as the Biermann battery and originally studied in the context of stars (Biermann 1950) was considered
    in the cosmological context by Pudritz and Silk (1989); Kulsrud et al. (1997); Davies and Widrow (2000) and Xu et al. (2008). A simple order of magnitude estimate yields:

    Now, I am not familiar with the Biermann battery, actually never heard about it before, but as I know the last author I am sure it is something appropriate.

    So, I am not really sure how a paper on the earliest magnetic fields in the universe combines with the "electrostatic collapse" model of CC.

    ETA apparently I cannot get my LaTeX correct here, I don't see the mistake though.
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    Quote Originally Posted by utesfan100 View Post
    Sorry for my ignorance. My understanding was that the giant molecular cloud was the remnants of a nova, as demonstrated by the abundance of metals in our solar system.
    The molecular cloud could be created by the remants of supernovae, and indeed, anything heavier that He basically has to have been created in the centre of a star. When this star explodes in a supernova it scatters its stuff into the surrounding part of the universe, enriching the interstellar region with metals.

    Now, a nova is something different. That is a accreting white dwarf in a double star system. The companion star loses mass to the compact white dwarf where it will generate an atmosphere. When the atmosphere reaches its critical point, i.e. enough mass has accreted and the density is favourable, then an explosive fusion event will burn up the atmosphere, brightening the compact star significantly, creating a "new" star labeled as a nova.
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    Quote Originally Posted by utesfan100 View Post
    Consider the Sun. It is believed to have formed from the nebula resulting from the nova of a protosun. This sun would have emitted electrons over its lifetime, making the nebula tend towards a net negative charge.
    This seems to be the T Tauri wind which is not a wind of electrons. It is a wind of nebula material emitted in two flows. The nebula was neutral. The wind should be neutral (neutral atoms, molecules, electrons and positive ions).

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    Searching the web (I don't have my Feynmann lectures here) the like attracts like seems to be experimentally verified for charged macro particles in fluids.
    I am not sure yet, whether we can expand this to dusty plasmas (and I don't have my dusty plasma book at hand either, being at home).
    More later, I hope.
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  17. #17
    As a favor for tusenfem, here's the LaTeX from the Widrow paper (just with the newlines removed).



    I don't doubt that this is a respectable force, but I'm still looking for the explanation of how this exerts a body force on the entire cloud. Vorticity at pressure and density gradients should be local to those boundary conditions. Maybe it's in there somewhere. Anyway, tusenfem is right -- this has nothing to do with what I'm proposing.

    Quote Originally Posted by Reality Check View Post
    Your "electrostatics" cannot balance the hydrostatic pressure of the gas as far as I can see.
    OK, I'm not showing any maths in support of these contentions -- I just wanted to sanity-check the idea first. (You never know who is two steps ahead of you until you open your mouth... ) But there are anomalies in the gravity model. If you compress a gas, the pressure and temperature go up, while G gets more dense. Gravity obeys the inverse square law, while the hydrostatic pressure increases as a linear function of volume. So there is a threshold beyond which G takes over. (At least that's my over-simplified understanding of it.) But given the same parameters, sometimes gas clouds condense, and sometimes they don't. Absorbing the ejecta from a supernova increases the mass of the cloud, but also the temperature, and both as a direct function of the mass of the ejecta that are absorbed. So this doesn't necessarily put the cloud any closer to the Jeans instability. That leaves open the possibility that other force(s) are present. E might be a subtle force in this context, and I'm certainly not talking about it as the sole, or even the primary, reason for the accretion. I'm just saying that it might help account for the anomalies, and it seems to have the right properties.

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    Thanks for the LaTeX, I will refrain from <cr>s from now on.

    However this seems that you are just swimming here with your ideas, which is not allowed under the ATM rules. Maybe you should first develop this more, including the math, and then be ready to present a model and defend it.

    Thread closed.
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