"Why Lower Corona of the Sun Is Hotter Than the Photosphere"

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MosaicDave
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"Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by MosaicDave » Wed May 19, 2010 7:28 am

In relation to EU perspectives on the Sun's assumed temperature profile, I've several times seen it proposed that an accelerated stream of ions becomes "dethermalized". And in this TPOD, here is the concept again:
As these positive ions accelerate down the steep potential energy drop, they exchange the high (electrical) potential energy they had in the photosphere into kinetic energy – they gain extremely high outward radial velocity and lose side-to-side random motion. Thus they become "de-thermalized." This is because in this region of high radial acceleration, the movement of these ions becomes extremely organized (parallel). Their temperature, which is just a measure of their random motion, drops to a minimum.
I don't believe this idea makes any sense. This is like saying that if you spray hot water out of a hose, it somehow cools down as a result of being accelerated. Or, that if you transport a cup of hot coffee at high speed on an airplane, that it somehow becomes "de-thermalized".

I could accept that cooling might occur as a result of some type of adiabatic process, though I haven't worked out any of the numbers relating to the assumed densities and temperatures and so forth, in relation to the Sun. But there's no basis for accelerated ions to "lose side-to-side random motion" purely as a result of acceleration.

As a disclaimer, I'm completely convinced of the ubiquitous and fundamental involvement of electromagnetic effects in the operation of the Sun, and the rest of the cosmos as well; I believe this is undeniable by anyone open minded enough to look at even some of the overwhelming evidence. And, Donald Scott's great web site was in fact my own first eye-opening introduction to Ralph Juergens and the matrix of EU concepts. But I believe the notion of "dethermalization" in this context is an error.

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solrey
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Re: "Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by solrey » Wed May 19, 2010 11:05 am

Dethermalization in that context is exactly right. There's a difference between heat and temperature. For molecules, atoms, ions and electrons, heat is the combined potential and kinetic energy available, measured in electron volts in the case of plasma. Temperature is the kinetic energy, transferred to other atoms and molecules in collisions, typically measured in kelvin or celsius. Generally temperature and heat coincide except in a few special cases. The boiling point of a substance is one example where the extra heat energy beyond the boiling point goes into breaking more bonds instead of increased collisions. Heat can be transmitted through electromagnetic radiation, like infrared and ultraviolet, or kinetically in collisions.

In the case of a plasma, a strong electric field will reduce the collisions that transfer kinetic energy so the energy that is transferred is mostly in the form of electromagnetic radiation. Getting an x-ray is kind of similar where the heat energy is transferred as electromagnetic radiation while the temperature of the emitter stays relatively cool. Laser cooling is a technique that uses the energy of laser light from opposing directions which allow atoms in a gas to maintain their positions instead of colliding randomly, effectively cooling the gas.

I hope I that's not too confusing. :?
“Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality"
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jjohnson
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Re: "Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by jjohnson » Wed May 19, 2010 12:50 pm

there's no basis for accelerated ions to "lose side-to-side random motion" purely as a result of acceleration.
The basis of Don Scott's explanation is that a charged particle in motion in a magnetic field experiences a force at right angles to its velocity vector, with a magnitude proportional to the particle's charge (Q), the velocity vector and the magnetic flux density: F = QU x B

The turning force applied by the magnetic field causes the charged particle to assume a circular motion around an imaginary field line, coupled with whatever axial motion it started out with when entering the field, if any. This leads to a path with a helical shape in 3D space. If the magnetic field changes direction, so too does the helical path of particles riding along it. The electric field potential (volts per meter) is what accelerates the particle parallel to the magnetic lines of equal potential, and where the axial energy increase comes from.

The local magnetic field of the plasma requires more energy from charged particles in motion to move transversely across the lines of magnetic potential than parallel to them. A force is applied to such particles (ions and electrons) to turn them away from their traversing the (imaginary) magnetic field lines and to continue to accelerate them parallel with the field lines. This velocity vector acceleration increases the magnetic field strength, which in turn is able to provide a higher resistance to particles' transverse velocity components. The more parallel they move, the fewer the number of collisions per unit time, and less energy involved in the few glancing, near-parallel collisions. This is dethermalization. Random or Brownian motion gets suppressed or minimized by the steering electromagnetic fields which "parallelize" their flow. The bulb of the ol' solar thermometer (moving with the flow) is not hit as often nor as hard, while the particles themselves stream faster and faster (have more kinetic energy in eV) along the field lines' direction.

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Re: "Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by MosaicDave » Wed May 19, 2010 10:50 pm

jjohnson--

Wow, thanks for that excellent explanation; that makes sense now.

Don Scott's dethermalization argument had sort of bugged me for a long time, but I hadn't been thinking about the magnetic field effects...

--dc

(EDIT: More thoughts in subsequent post...)
Last edited by MosaicDave on Wed May 19, 2010 11:03 pm, edited 1 time in total.

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Re: "Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by MosaicDave » Wed May 19, 2010 11:02 pm

jjohnson--

Now, thinking about this more, I find I'm still not happy with this explanation of "dethermalization". Here's why:

The effect you're describing, is what induces charged particles to spiral when traveling along an axial magnetic field. But still, there's no mechanism to absorb the transverse momentum. F = QU x B is just causing a perpendicular force that induces a particle to change direction and travel in a circle or spiral, as the case may be; however it doesn't slow the particle down...

Whatcha think?

--dc

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Re: "Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by jjohnson » Fri May 21, 2010 10:06 am

It may not slow the particle down (it doesn't, in fact; it's an angular, not linear, acceleration). Momentum has to be conserved unless acted upon by an outside force, but perhaps a portion of the linear momentum is converted to angular momentum, or perhaps the energy input by the magnetic field is radiated away by the particle by releasing the required photon quanta to compensate (if it is an electron, anyway).

But by confining a particle to move within a certain transverse radius (the radius it asumes in its helical orbit) it restricts it from going any farther than that radius, so its field of possible lateral interaction with particles is suddenly suppressed to that distance. If the plasma is sparse, the particle's range of interaction tends to make those interactions occur with the most nearby field aligned particles. Its mean free path becomes much longer (average time between collisions or interactions with other particles). There's plenty of those, as thermal temperatures can indicate. And since particles are tending to follow aligned helices, even if they intersect or even involve the "same" filed line, what are the probabilities that two particles moving along the same cylindrical (magnetic equipotential) surface, that the timing and spacing of their paths will intersect? ( I can't compute it either, frankly, but it trends down in a hurry. Cars on a multi-lane freeway tend to collide a lot fewer times per second than cars in a destruction derby!)

Note that heavy charged particles will have a larger radius than the lighter electrons, which could increase their "cross-section" probability of interactions, and positive charges like protons or ionized molecules are likely accelerating in the anti-parallel direction from the negative charges, increasing the energy of collision. Plasmas can exhibit two different temperatures, thermal and kinetic, with the KE of dethermalized particles moving at times at relativistic velocity significantly greater than that of Brownian collision. Keep in mind that I am just thinking out loud here.
Jim

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Re: "Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by MosaicDave » Mon May 24, 2010 7:08 am

So I've been thinking about this a lot: Using my right hand, and my trusty right hand rules, to imagine the magnetic field around a filament of current, and to think about the Lorentz force on a charged particle that tries to move transversely through this field, and how it's path might thereby be induced to curve...

I can sort of imagine, how this kind of transverse momentum might get redirected to be parallel to the main channel of conduction, and how at the same time the particle could tend to be drawn back into the main channel...

Which, I suppose, is how a Birkeland current must self-organize...

But, it's extremely confusing and uncertain to think about. So I'm wondering - are there other examples where this kind of electromagnetically induced "dethermalization" is observed to occur? Maybe this happens inside cyclotrons and particle accelerators, so that a beam forms out of a disorganized plasma? Maybe there are other examples?
jjohnson wrote:Cars on a multi-lane freeway tend to collide a lot fewer times per second than cars in a destruction derby!
Well, yes... But if you have a bunch of bumper cars with springy bumpers just bouncing off each other brownian-style, and you just accelerate them in some direction as a group, then they'll still keep on bumping just the same, only they'll be traveling in some direction as a group while doing it. So my original point, was that there has to be some mechanism to remove transverse momentum from the system, if "dethermalization" is to occur.

Now, I can sort of see how the Lorentz force / q(vxB) could accomplish this. But when I try to imagine how it works, it quickly becomes tremendously, fantastically confusing... Maybe this is why Anthony Perratt had to run particle-in-cell simulations on supercomputers to study this stuff?

All for now--

--dc

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Re: "Why Lower Corona of the Sun Is Hotter Than the Photosphere"

Unread post by GaryN » Sat May 29, 2010 11:20 am

This page has some proposals and explanations for the heating of the solar atmosphere:

http://scicollege.net/archives/88/
In order to change an existing paradigm you do not struggle to try and change the problematic model. You create a new model and make the old one obsolete. -Buckminster Fuller

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