Magnetic reconnection and physical processes

[Tubbythin]

Who give a twaddle about computing power!!!!

What on Earth do you mean? Our computing power limits our ability to do computer simulations. It is probably the single-most important factor in deciding how to model a complex system! It couldn't be more relevant.

 

[Tubbythin]

I never said it was odd. Its just that the Ev is the most convenient unit (ok, for me)when talking particles that move.

You said the eV was a fundamental unit. You were wrong. You said the eV was defined in relation to the foot. You were wrong. This was pointed out. How does that constitute nitpicking?

 

[Tim Thompson]

Is MHD Misapplied?

Someday you will be able to run a complete PIC simulation with the physical layout of the flux tubes.

And when we do the results will be the same as they were in the MHD simulations, within the bounds of numerical & observational uncertainty. There will be no instance of any significant result achieved by MHD which will be nullified by PIC simulations.

You said this:

I never said MHD was wrong, its just being misapplied.

Prove it. Show us one example of a result from the current literature, derived from MHD, which will be nullified by PIC simulations. Show us explicitly that MHD is in fact being misapplied.

 

[sol invictus]

Show us one example of a result from the current literature, derived from MHD, which will be nullified by PIC simulations. Show us explicitly that MHD is in fact being misapplied.

Not long ago I was speaking to an internationally known expert on numerical simulations of plasma physics. He told me that MHD seems to work very well even in regimes where one would expect it to break down (like when the plasma is extremely diffuse), and that PIC simulations are being used to try to understand why it works so well even when it "shouldn't".

Bottom line - MHD is an extremely good approximation when it's expected to be, and often an extremely good approximation even when it's not expected to be.

 

[Michael Mozina]

Not long ago I was speaking to an internationally known expert on numerical simulations of plasma physics. He told me that MHD seems to work very well even in regimes where one would expect it to break down (like when the plasma is extremely diffuse), and that PIC simulations are being used to try to understand why it works so well even when it "shouldn't".

Bottom line - MHD is an extremely good approximation when it's expected to be, and often an extremely good approximation even when it's not expected to be.

All of that is true of course, but there are still two ways to describe MHD theory, from what Alfven called the "particle/circuit" (E) orientation, or from what Alfven called the "field" or (B) orientation. Why you would choose to call a short circuit between two current carrying filaments a "magnetic reconnection" event is simply beyond me. It's like calling any discharge event, or any short circuit a "magnetic reconnect" process simply because the magnetic field topology changes over time. You still have the magnetic cart before the electric horse. It doesn't work so well that way sol.

Rhessi has already identified a "natural" source of gamma ray emissions from electrical discharges in the Earth's atmosphere. It sees exactly the same gamma ray emissions from the solar atmosphere, and the most likely 'cause' is the natural one that occurs here too. Like I said, you still have the magnetic cart before the electric horse.

 

[sol invictus]

Why you would choose to call a short circuit between two current carrying filaments a "magnetic reconnection" event is simply beyond me.

I don't and never have. None of the examples of magnetic reconnection we've discussed involve any short circuit, nor does current flow along the reconnecting lines.

It's like calling any discharge event, or any short circuit a "magnetic reconnect" process simply because the magnetic field topology changes over time. You still have the magnetic cart before the electric horse. It doesn't work so well that way sol.

You have absolutely no idea how it works, Michael.

 

[brantc]

What on Earth do you mean? Our computing power limits our ability to do computer simulations. It is probably the single-most important factor in deciding how to model a complex system! It couldn't be more relevant.

LOL, since my pencil is not sharp I cant do calculations.........

I am talking about accuracy of methods of simulation.
If you have enough money you can do some amazing things with computers!!

 

[brantc]

You said the eV was a fundamental unit. You were wrong. You said the eV was defined in relation to the foot. You were wrong. This was pointed out. How does that constitute nitpicking?

Yep. I'm wrong. The worlds going to end. I make mistakes.....

 

[brantc]

And when we do the results will be the same as they were in the MHD simulations, within the bounds of numerical & observational uncertainty. There will be no instance of any significant result achieved by MHD which will be nullified by PIC simulations.

You said this:

Originally Posted by brantc View Post
I never said MHD was wrong, its just being misapplied.

Prove it. Show us one example of a result from the current literature, derived from MHD, which will be nullified by PIC simulations. Show us explicitly that MHD is in fact being misapplied.

MHD does not correctly predict the structure of certain field aligned flux tubes.

Show me the latest paper you have for MHD flux tubes. Or the best model or predictions.

I will then show you an observation(feature) that has not appeared in MHD simulations.
And I observed it and told somebody, and I just repeated that observation not too long ago.

 

[Reality Check]

MHD does not correctly predict the structure of certain field aligned flux tubes.

First asked 24 February 2010
brantc,
Can you give a citation for your source for "MHD does not correctly predict the structure of certain field aligned flux tubes"?

Show me the latest paper you have for MHD flux tubes. Or the best model or predictions.

Nonlinear propagation of Alfven waves driven by observed photospheric motions: Application to the coronal heating and spicule formation

I will then show you an observation(feature) that has not appeared in MHD simulations.
And I observed it and told somebody, and I just repeated that observation not too long ago.

Why not give it now.
How do you know that this "observation(feature)" has not appeared in MHD simulations?
I assume that this "observation(feature)" falls into the category of things that should appear in MHD simulations.

 

[Tim Thompson]

Is MHD Misapplied? II

You said this:

I never said MHD was wrong, its just being misapplied.

Prove it. Show us one example of a result from the current literature, derived from MHD, which will be nullified by PIC simulations. Show us explicitly that MHD is in fact being misapplied.

Show me the latest paper you have for MHD flux tubes.

No. You made the claim, now back it up. If you can't show us on your own a clear example of MHD being misapplied in today's literature then you have nothing at all to say that is worth paying attention to.

 

[Tubbythin]

LOL, since my pencil is not sharp I cant do calculations.........

I am talking about accuracy of methods of simulation.
If you have enough money you can do some amazing things with computers!!

You can model, say, a mole of gas on an individual particle basis?

 

[Tubbythin]

Yep. I'm wrong. The worlds going to end. I make mistakes.....

Everyone makes mistakes. I don't have a problem with that. Its the fact that you choose to accuse others of nitpicking when they point out your mistakes. Here is what you said originally:

If you think about how electron(or particle energy) is measured, it is measured in Electron Volts.

This is 1 volt across 1 foot. That is a measure of velocity. This is the fundamental measurement of energy.
Everything can be decomposed to the electron volt as a measure of wavelength.

This is a measure of kinetic energy. Thats why I think of everything in kinetic energy. It works.

Does the kinetic energy account for reconnection in the flux tubes in the LAPD? Here it seems that it does.
And there is no flux tube until the LPP is produced!!!!

Clearly, pointing out that you are completely isn't simply nitpicking around some trivial detail of a larger argument, its pointing out that your whole larger argument is completely wrong.

 

[brantc]

No. You made the claim, now back it up. If you can't show us on your own a clear example of MHD being misapplied in today's literature then you have nothing at all to say that is worth paying attention to.

You show me the latest work. Why?
Because I have gone through this before. I show something and then I'm told this is not the latest, or its wrong because I picked the wrong paper or whatever. Never again!!


So I going to leave it up to you as to what you want me to "refute".
You pick an example/paper/simulation and I will show you where its misapplied/or features not taken into account.

It should be easy for you Tim, since you are right and an expert.

If I cant I will clearly admit I was wrong.

 

[brantc]

Everyone makes mistakes. I don't have a problem with that. Its the fact that you choose to accuse others of nitpicking when they point out your mistakes. Here is what you said originally:



Clearly, pointing out that you are completely isn't simply nitpicking around some trivial detail of a larger argument, its pointing out that your whole larger argument is completely wrong.

So "1 foot" and "fundamental unit" makes everything else I said wrong??

Lets apply that to other scientists with equal zeal.

 

[DazzaD]

So "1 foot" and "fundamental unit" makes everything else I said wrong??

Lets apply that to other scientists with equal zeal.

No. Of course not.

BUT

if one of my students seriously contends that 2 times 7 is damn well 29 and not anything else and it couldnt possibly be, even after handing them a calculator and a pencil, and if they then go on to claim they have solved a difficult algebraic puzzle that I had trouble with myself, I think I would have serious doubts about them being able to do it.

Its human nature and its also sensible (in most cases).

I think its perfectly reasonable for a technical subject such as magnetic reconnection to establish that we are "all on the same page" with regards to what we understand in physics and mathematics.

It is not easy to explain/show the details of quantum mechanics to an A Level student simply because their mathematical ability has not quite got up to the level where they could clearly understand it.

It is reasonable to keep a check on each others understanding of basic physics in order that we dont confuse or talk over each other.

 

[Reality Check]

So I going to leave it up to you as to what you want me to "refute".

Tim's statement is correct. You are the one with the claim:

Originally Posted by brantc
MHD does not correctly predict the structure of certain field aligned flux tubes.

and so strictly speaking it is up to you to back it up. This has the advantage that you can find the papers on the "certain field aligned flux tubes" and not bother about all of the 1000's of other papers where MHD works.

You pick an example/paper/simulation and I will show you where its misapplied/or features not taken into account.

Now it looks like you think that any random example/paper/simulation will contain misapplied MHD or features not taken into account.
Here is a random paper that I found (there are lots more) and presented to you yesterday:
Nonlinear propagation of Alfven waves driven by observed photospheric motions: Application to the coronal heating and spicule formation

Waiting for your reply ...

 

[Tim Thompson]

Is MHD Misapplied? III

Because I have gone through this before. I show something and then I'm told this is not the latest, or its wrong because I picked the wrong paper or whatever. Never again!!

OK. So, you have already tried to support your claim, and you have been properly refuted every time. Hence, a lack of desire to continue trying to support your own claim.

If I cant I will clearly admit I was wrong.

And why would I believe that? After all, you just got finished explicitly admitting that every one of your "proofs" has been refuted, yet you still will not admit that it is even possible for you to be wrong.

No, the ball is where it belongs, in your court, and there it stays. if you are ready to quit, then quit. If you are ready to prove your claim, then prove it. Or perhaps you should simply admit that you have no idea what you are talking about and don't even know how to look for papers or studies which might support your claim.

So "1 foot" and "fundamental unit" makes everything else I said wrong??

I would say not wrong, simply unreliable. The sloppy use of language in any discussion usually stems from ignorance. People who know what they are talking about also know what language, jargon & vocabulary to use while they are talking about it, so other people working the same field will have a precise understanding of what is being said. People who do not know what they are talking about also do not know how to talk about it. So they use the language they do know in a sloppy manner, or invent language that nobody will understand except themselves. Your sloppy language indicates sloppy thinking and ignorance. Once you have projected that kind of persona, it is very hard to reverse the effect.

 

[Tubbythin]

So "1 foot" and "fundamental unit" makes everything else I said wrong??

Lets apply that to other scientists with equal zeal.

Everything you've said ever? No. The point you were trying to make in the text I quoted? Yes.

 

[Michael Mozina]

It is reasonable to keep a check on each others understanding of basic physics in order that we dont confuse or talk over each other.

Yes, but your brand of "physics" is something Alfven himself referred to as "pseudoscience". Worse yet, none of you seem to be able to explain what is unique in terms of the actual "physics" involved in "magnetic reconnection' that is physically distinguishable from induction and ordinary particle collisions in "current carrying" plasma. There is no "physics" offered by your side, just a "dumbed down" B field mathematical rendition of a "circuit reconnection" process.