Is there plasma that doesn't radiate visible light? I think the

[Varon]

Is there plasma that doesn't radiate visible light? I think the electrons falling back to the nucleus radiate visible photons. But what if the plasma only has particles that are not atoms?

 

[rsr_life]

Particles that are "not atoms"? Could you give us an example of what you have in mind?

 

[Drakkith]

Particles that are "not atoms"? Could you give us an example of what you have in mind?

I think he means that the particles in a plasma aren't bound into atoms, so do they radiate light. I believe they will emit various wavelengths of light due to accelerations of electrically charged particles. But I'm not sure.

 

[Varon]

Yes.. particles in plasma that aren't bound to atoms... what if they are not charged.. then they won't radiate? Or do all plasma contain charged particles?

 

[Drakkith]

Yes.. particles in plasma that aren't bound to atoms... what if they are not charged.. then they won't radiate? Or do all plasma contain charged particles?

You will not have a plasma on Earth that isn't made up of charged particles. The only place that could would be inside massive objects such as stars. And even then not really, as a free neutron has a half life of 15 minutes.

 

[Varon]

What are examples of plasmas that only contain electrons? Since there is no nucleus to make it fall to lower state, then no photons would be radiated, right? Then this plasma is totally invisible to visible spectrum?

 

[ZapperZ]

What are examples of plasmas that only contain electrons? Since there is no nucleus to make it fall to lower state, then no photons would be radiated, right? Then this plasma is totally invisible to visible spectrum?

Er... an atomic transition is NOT the only way to create light. A charge particle being accelerated is another example. What do you think synchrotron light sources are? Or what about free electron lasers? You pass bunches of electrons through something that causes it to wiggle up and down, and viola! You get light!

Zz.

 

[Varon]

i see. what plasma sources have both nucleus and electrons in the plasma and what plasma sources have pure ions only? Any site with a list of them?

 

[ZapperZ]

i see. what plasma sources have both nucleus and electrons in the plasma

Your fluorescent lamps.

and what plasma sources have pure ions only?

The ion beam at RHIC, ion beam milling equipment, etc.. etc.

Zz.

 

[sophiecentaur]

Your fluorescent lamps.



The ion beam at RHIC, ion beam milling equipment, etc.. etc.

Zz.

I thought that a plasma was defined as having net neutral charge.

 

[ZapperZ]

I thought that a plasma was defined as having net neutral charge.

I don't think that's a necessary criteria, is it?

If it is, then asking for "ion beam plasma" would be an oxymoron, which probably won't surprise me.

Zz.

 

[Dotini]

Is there plasma that doesn't radiate visible light? I think the electrons falling back to the nucleus radiate visible photons. But what if the plasma only has particles that are not atoms?

Does solar wind radiate visible light? How about a household air ionizer?

Respectfully,
Steve

 

[sophiecentaur]

I don't think that's a necessary criteria, is it?

If it is, then asking for "ion beam plasma" would be an oxymoron, which probably won't surprise me.

Zz.

I wouldn't normally just quote Wikkers but they, and a few other more raggedy sites, seem to reckon that a plasma is overall neutrally charged.

It wouldn't be the first oxymoron I'd come across!

 

[Varon]

Wiki entry on Plasma stated:

"Definition of a plasma

Plasma is loosely described as an electrically neutral medium of positive and negative particles (i.e. the overall charge of a plasma is roughly zero)."

Is this true?

So overall charge is roughly zero for plasma composed of atoms? And for those composed only of ions.. it's negative charge? Is this correct? So how do each of them (neutral and charged) behave? What is the major (dramatic) difference between them aside from charge?

 

[sophiecentaur]

How can you conclude that a plasma can consist of only Ions if you are quoting an article saying a plasma is neutral?

 

[Varon]

Zapper mentions about ion plasma beam.. which I assumed is negative charged since it is composed of electrons

 

[sophiecentaur]

You are assuming Zapper is correct?

 

[Varon]

You are assuming Zapper is correct?

He is PF Mentor, How could he be wrong. If he is not sure, he would say not sure.

 

[ZapperZ]

Er... being a PF Mentor doesn't make it right all the time. In fact, I think sophiecentaur may have a more accurate definition of a "plasma" than what I had assumed.

Zz.

 

[ZapperZ]

Zapper mentions about ion plasma beam.. which I assumed is negative charged since it is composed of electrons

Er... "ion beam" is composed of ions, not electrons.

You asked for a "plasma" consisting only of ions, and I gave you an ion beam. This may or may not be a valid example of a "plasma". That's why if a plasma is a net neutral gas, I said that asking for an "ion plasma" is an oxymoron.

Zz.

 

[Varon]

Er... "ion beam" is composed of ions, not electrons.

You asked for a "plasma" consisting only of ions, and I gave you an ion beam. This may or may not be a valid example of a "plasma". That's why if a plasma is a net neutral gas, I said that asking for an "ion plasma" is an oxymoron.

Zz.

Oh. I thought an electron is an ion. Anyway, wiki says:

"An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative".

Can plasma can be composed of positive or negative ions?

 

[Drakkith]

Oh. I thought an electron is an ion. Anyway, wiki says:

"An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative".

Can plasma can be composed of positive or negative ions?

Here's my look on it.

Generally speaking, an Ion is an atom, or at least a nucleus of an atom. A single electron isn't generally considered an Ion since it is a fundamental particle, while Ions in plasmas can be anything from 1 proton to heavy nuclei consisting of tens - hundreds of nucleons. This gives rise to calling electrons in plasma by their actual name and calling the nuclei by the term Ions, since calling them anything else doesn't really make sense to me. Also, calling an electron an Ion would probably add confusion when talking about plasmas since they are negatively charged while the protons and nuclei are positive. Probably just another way to help differentiate the two charges in plasmas.

 

[sophiecentaur]

Has anyone mentioned that only positive ions could exist in a plasma because the temperature will mean that passing electrons cannot get captured by an atom. Their energy will be too high.

 

[Drakkith]

Has anyone mentioned that only positive ions could exist in a plasma because the temperature will mean that passing electrons cannot get captured by an atom. Their energy will be too high.

If not, then you just did!

 

[Varon]

In my earlier message. I asked if plasma can contain ions only (at that time I thought ions are electrons) so I didn't get the answer I seek. So let me ask again, can plasma be composed of electrons only? What if you get a group of electrons and heat them... won't they be plasma?

 

[Drakkith]

In my earlier message. I asked if plasma can contain ions only (at that time I thought ions are electrons) so I didn't get the answer I seek. So let me ask again, can plasma be composed of electrons only? What if you get a group of electrons and heat them... won't they be plasma?

Offhand I would call that plasma, but I am unsure about the scientific/technical world.

 

[Drakkith]

Honestly, does it really matter what its CALLED? Is that all you were wanting to know or did you have something else to go along with that?

 

[sophiecentaur]

Did you not read the definition of a plasma? If you did then did you not get the bit about electrical neutrality? If a plasma is neutral then don't you need both positive and negative charges in there?
How did you intend to get the electrons to all stay together without some positive ions around to stop them drifting off?

 

[sophiecentaur]

Honestly, does it really matter what its CALLED?

Perhaps not but if we aren't all talking with the same terms then any conversation is a bit limited.
Certainly there is a huge difference between a neutral mixture and a large group of particles all with the same charge.

 

[Varon]

Did you not read the definition of a plasma? If you did then did you not get the bit about electrical neutrality? If a plasma is neutral then don't you need both positive and negative charges in there?
How did you intend to get the electrons to all stay together without some positive ions around to stop them drifting off?

Ok. I just heard some theorize that dark matter is composed of plasma and wondering what kind of unconvensional particles it may contain that don't react electromagnetically... or too subtle to be detected... they reported about magnetic field that exist right in the middle of nowhere in deep outer space... and wondered if they came from the dark matter plasma..

 

[Drakkith]

Ok. I just heard some theorize that dark matter is composed of plasma and wondering what kind of unconvensional particles it may contain that don't react electromagnetically... or too subtle to be detected... they reported about magnetic field that exist right in the middle of nowhere in deep outer space... and wondered if they came from the dark matter plasma..

Well, remember that like charges repel, so any "plasma" that doesn't consist of equal amounts of charges (ions and electrons) will fling itself apart.

 

[Varon]

Well, remember that like charges repel, so any "plasma" that doesn't consist of equal amounts of charges (ions and electrons) will fling itself apart.

Check this out:

http://arxiv.org/abs/0810.5126

Can you try to refute the article?

"We raise the prospect of interesting new plasma effects in dark matter dynamics, which remain to be explored. "

 

[ZapperZ]

Check this out:

http://arxiv.org/abs/0810.5126

Can you try to refute the article?

"We raise the prospect of interesting new plasma effects in dark matter dynamics, which remain to be explored. "

This is a meaningless reference. You are using something that is still a "research front" (dark matter) as "evidence".

You shouldn't be trolling such papers when you are having problems with understanding basic physics.

Zz.

 

[Varon]

This is a meaningless reference. You are using something that is still a "research front" (dark matter) as "evidence".

You shouldn't be trolling such papers when you are having problems with understanding basic physics.

Zz.

The reason I started this thread is to understand plasma better in order I can scrutinize the paper myself. So I may share the paper as well.

Anyway. What I learn here is the plasma should always have positive and negative charge. Now that part of the paper makes sense.. that dark matter can only be plasma if there is dark radiation made up of positive and negative charge too. So you guys are helpful in this realization. Thanks.

 

[ZapperZ]

The reason I started this thread is to understand plasma better in order I can scrutinize the paper myself. So I may share the paper as well.

Anyway. What I learn here is the plasma should always have positive and negative charge. Now that part of the paper makes sense.. that dark matter can only be plasma if there is dark radiation made up of positive and negative charge too. So you guys are helpful in this realization. Thanks.

And that makes very little sense, because you clearly have not understood what "dark matter" is. If it is a plasma, we would have observed it very clearly. After all, we HAVE observed plasma in other parts of the universe!

You are trying to learn physics in bits and pieces, and I've noticed this in many of your posts on here. I don't think you have a coherent understanding of the physics that you're asking about. This thread is one clear example where you're think you've understood something, when clearly, you missed the complete picture. It is very difficult to comprehend that for someone who didn't know what an "ion" is, that you're are attempting to understand papers like this.

Zz.

 

[Varon]

And that makes very little sense, because you clearly have not understood what "dark matter" is. If it is a plasma, we would have observed it very clearly. After all, we HAVE observed plasma in other parts of the universe!

You are trying to learn physics in bits and pieces, and I've noticed this in many of your posts on here. I don't think you have a coherent understanding of the physics that you're asking about. This thread is one clear example where you're think you've understood something, when clearly, you missed the complete picture. It is very difficult to comprehend that for someone who didn't know what an "ion" is, that you're are attempting to understand papers like this.

Zz.

I know what is dark matter.. we don't know what it is composed of.. whether the lightest supersymetric particles or others we don't know. The paper is just proposing it is some kind of plasma and I've been thinking about it for months on and off so may as well ask about plasma here. Btw.. i own over a hundred pop-sci science books and read all of them (mostly mathless hence I focus more on the conceptual as I'm still learning the math) .

Anyway. Here's the abstract of the paper:

"We explore the feasibility and astrophysical consequences of a new long-range U(1) gauge field
(dark electromagnetism") that couples only to dark matter, not to the Standard Model. The
dark matter consists of an equal number of positive and negative charges under the new force,
but annihilations are suppressed if the dark matter mass is sufficiently high and the dark fine structure constant ^ is sufficiently small. The correct relic abundance can be obtained if the dark matter also couples to the conventional weak interactions, and we verify that this is consistent with particle-physics constraints. The primary limit on ^ comes from the demand that the dark matter be eectively collisionless in galactic dynamics, which implies ^ <
103 for TeV-scale dark matter. These values are easily compatible with constraints from structure formation and primordial nucleosynthesis. We raise the prospect of interesting new plasma eects in dark matter dynamics, which remain to be explored."

 

[ZapperZ]

If you wish to discuss dark matter, then please do so in the appropriate forum.

I have no idea why you would copy the abstract here. It's not as if I can't click a link and read it myself.

This thread is done.

Zz.