Electricity's role in astrophysics

[Northwind]

This is more of a consensus type question that a true Q&A and I'll try and word it so as not to make it sound like an ATM thread.

What is electricity wrt astrophysics? how is it modeled?

What significance does it play in astrophysical phenomena?

How well do "accepted" theories incorporate "electricity" and it's effects in objects like BH, neutron stars, pulsars, galactic jets, T-turi stars, variable stars, normal main sequence stars, dark matter, dark energy etc etc?

How well do "accepted" theories incorperate/model such dynamic electrical phenomena into their respective mathematical equations? a little? alot? not at all?

Does electricity play any role in space besides making pretty "lights"? i.e. does it do any "work"?

Does a flow of charged particles constitute "electricity"?

Is an object, spaceprobe, asteroid, moon, planet able to collect a "charge"?

Lots more question but enough for now.

Thoughts?

[Maksutov]

Thoughts?

My thought is this appears to be yet another incursion of ATM material into the Q&A forum.

Not that the OP would have any interest in such things.

[Tobin Dax]

Northwind, how are you defining electricity? Your use of quotes, among other things, makes me unsure that I understand what you're asking.

[01101001]

Not that the OP would have any interest in such things.

I think that's an expired search-id link. That's OK. I'll imagine something horrid.

[Eta C]

Thoughts?

Get out and do some real reading instead of placing any credence in websites such as Thornhill's "Thunderbolts." Thornhill is "not even wrong" to parapharase one of my favorites.

Recommended reading: Russell M. Kulsrud's textbook "Plasma Physics for Astrophysics." It describes how plasma physics fits into modern cosmological theories. I think you'll find that the field is not the "forbidden zone" Thornhill and other PU types try to make it into in their paranoia. A brief search on Amazon should also turn up other books that should answer your questions.

[Jeff Root]

This is more of a consensus type question that a true Q&A and I'll
try and word it so as not to make it sound like an ATM thread.

I can totally ignore any possible ATM slant as I don't know
anything about it. So I'll treat these as straight questions.

What is electricity wrt astrophysics? how is it modeled?

Exactly the same as electricity in any other area of study.
Maxwell's equations are an adequate description of many electric
and magnetic phenomenon. When a quantum description is needed,
quantum electrodynamics (QED), developed in the 1940's, gives
predictions as accurate and precise as the values you input into
the calculations. It is the most precise and well-confirmed
theory in all of science.

What significance does it play in astrophysical phenomena?

It determines everything about how atoms and ions interact with
each other, which is most of physics and practically all of
chemistry. It determines the temperatures of all things, what
light they give off, reflect, transmit, or absorb, whether they
bounce off of each other or stick together when they collide --
almost everything.

How well do "accepted" theories incorporate "electricity" and
it's effects in objects like BH, neutron stars, pulsars, galactic
jets, T-turi stars, variable stars, normal main sequence stars,
dark matter, dark energy etc etc?

We only know about any of those things because of the many and
varied effects of electric forces. Electric forces generate all
the light that allows us to see stars, gas, dust, and jets, and
deduce the existence of things we can't see, such as black holes,
dark matter, and dark energy. The way the light is generated
and the way the light is modified before it reaches Earth tells
us everything we know about the objects.

How well do "accepted" theories incorperate/model such dynamic
electrical phenomena into their respective mathematical
equations? a little? alot? not at all?

The only way to answer this question is for you to learn about
each of the theories you are wondering about. Electrodynamics
will tell you a lot about what is going on inside and on the
surface of a main-sequence star, while it can say very little
of significance about what is going on in a black hole. Dark
matter is an astonishing discovery precisely because it does
not interact with other matter via the electric force. And for
precisely that reason, we know almost nothing about it.

Does electricity play any role in space besides making pretty
"lights"? i.e. does it do any "work"?

Electric forces are the basis of chemistry. Electric forces
are what keep stars from instantly collapsing to black holes.
Electric forces are what carry the energy from the cores of
stars to their surfaces, and from there to everywhere else in
the Universe, including Earth.

Does a flow of charged particles constitute "electricity"?

That sounds reasonable. That is an electric current, of course.

Is an object, spaceprobe, asteroid, moon, planet able to collect
a "charge"?

Yes. Built-up charge and discharge of built up charge have been
problems on spacecraft. But the total charge in such cases is
quite small. Charges tend to flow to eliminate themselves. In
vacuum, it is a bit difficult to get a flow started, but if ions
are released from a material, they move easily and rapidly to a
region of opposite charge. Air is a pretty good insulator.
Vacuum is less good. An asteroid or planet could not build up
a large overall charge because opposite charges are attracted,
cancelling it.

-- Jeff, in Minneapolis

[Northwind]

Thankyou Jeff

[tusenfem]

electricity is defined as:

Any effect resulting from the existence of stationary or moving electric charges

From Concise Science Dictionary (Oxford Reference)

[Maksutov]

I think that's an expired search-id link. That's OK. I'll imagine something horrid.

Link fixed.

Thanks.

[antoniseb]

My thought is this appears to be yet another incursion of ATM material into the Q&A forum.

Until there is a dive into ATM in this thread, we will treat this as a sincere request to find out more about mainstream positions on electricity and magnetism in astrophysical phenomena. We welcome this, in part, because there are people new to astronomy who are unaware of these, and people with more experience who still have some misconceptions.

[Maksutov]

Until there is a dive into ATM in this thread, we will treat this as a sincere request to find out more about mainstream positions [on] electricity and magnetism in astrophysical phenomena. We welcome this, in part, because there are people new to astronomy who are unaware of these, and people with more experience who still have some misconceptions.

Fair enough.

Let's go.

Here's one course schedule that may serve as a guideline for the OP.

Then of course I have to include this.

I imagine a bit of the material has changed since I took some of these courses 40 years ago.

But the basics remain the same.

[Cougar]

What significance does [electricity] play in astrophysical phenomena?

• Gravity has always played a more significant role, and here's why: As mass is added, the attractive effect of gravity is increased. As more mass is added, the attractive effect is increased even more.
  
• As charged particles are added, their effect is typically lessened because, unlike gravity, there are both positive and negative charges, which neutralize each other's effect. As more charged particles are added, the odds are the overall effect will be further lessened by further such neutralization.

This is why electromagnetic phenomena demonstrated in a laboratory cannot be naively scaled up to galaxy-size effects.

[Universal Curiosity]

Just out of curiosity, what is an ATM thread?

[korjik]

Against the mainstream.

I am trying to change the useage when I say this. Electricity is the stuff in the wires that make the computers run and the lights turn on. There is no 'electricity' in astrophysics. There are plenty of electrical, electromagnetic, electrodynamic, and plasma effects tho.

Physics useage does not call all currents 'electricity.' That term is generally used only when talking about circiuts.

To directly answer the OP (again), Maxwells equations, then gravitation, are the base for ANY explanation of ANY effect in ANY physics process that is not dominated by quantum or relativistic effects. Even when the explanation needs to be quantum or relativistic, modified forms of both are the basis for the explanation. (The modified forms are actually the correct useage, but in most cases the additional math is unnecesary)

To summarize: 'electricity' is not a term used for astrophysical effects, but the basis for all electrical effects is the primary source for explanations of astrophysical processes.

[Tim Thompson]

To summarize: 'electricity' is not a term used for astrophysical effects, but the basis for all electrical effects is the primary source for explanations of astrophysical processes.

Korjik is right, so I want to make sure the caveat is well understood. We should be talking about electric fields and electric currents, that's the jargon you will see in astrophysics. The word electricity will never appear in astrophysics, as it is engineering & technology jargon. That said, we also need to remember that electricity is an electric current, it just happens to be confined by wires. And that is an important point to remember, because the wires strongly confine electricity, and strongly affect its behavior. Electric currents in astrophysics do not behave like electric currents in electricity, because they are not confined & restricted in the same way.

Now, before answering the several questions I would like to make a suggestion. Posting lists of questions like this is not a good idea. We can expect the thread to expand into an enormous & unwieldy affair, because there are so many questions pulling in so many directions. Q&A posts work a lot better if they are better focused. I will try to stick to the basics as much as possible to avoid that, but I think it is inevitable.

What is electricity wrt astrophysics? how is it modeled?

Electric currents are electric currents, and the electric currents of electricity (see caveat above) are modeled on exactly the same principles. In other words, a flow of charged particles. But electric currents in astrophysics are not confined by wires, so they are free to flow, in accordance with all of the other applicable laws of physics. Electric currents respond to electric & magnetic fields, but they also obey the laws of physics in general, and experience shows that the laws of fluid mechanics are usually (but not always) applicable. When they are, then the models are in accord with the principles of magnetohydrodynamics. At this point a more detailed answer would require at least a few hundred pages and falls outside the scope of this board.

But it is important to realize the electric currents of the type represented by electricity, namely a flow of charged particles which all have the same electric charge, are rare. In most cases, the current is charge neutral because there are no electric fields strong enough to promote significant charge separation. I am presuming you are interested in the kind of current I have mentioned here, a flow of like charged particles.

What significance does it play in astrophysical phenomena?

The significance, not surprisingly, depends entirely on the specifics of the moment. In some cases, electric currents are irrelevant, if they even are there. In other cases, they are significant, and must be included in any physical model. As I mentioned above, flows of like charged particles are rare, but not altogether absent. These "electricity" style currents flow in the solar photosphere, and in the magnetosphere of Earth. They also flow in a circuit that connects the solid earth to the magnetosphere and solar wind.

How well do "accepted" theories incorporate "electricity" and it's effects in objects like BH, neutron stars, pulsars, galactic jets, T-turi stars, variable stars, normal main sequence stars, dark matter, dark energy etc etc?

"How well" is an almost impossible question to answer. How is it possible to know "how well" without an absolute standard to measure against? If there are gaps in our knowledge (which there surely are), then how can we know "how well" our efforts are?

I won't try to answer "how well", but I will try to answer "how" to some small extent. Dark matter & dark energy have nothing at all to do with electric currents, nor any other apparition of electromagnetism. Black holes can have a net electric charge, and such black holes are theoretically modeled in the Riessner-Nordstrom theory. But one does not expect black holes to have any significant electric charge, and observation does not reveal any such black holes (although our ability to do so is probably limited). Stellar variabiltiy has nothing to do with electric currents, but does involve variable ionization. Likewise, electric currents are not relevant to T-Tauri stars. Electric currents are significant in the environs of neutron stars & pulsars, and can be significant in accretion disks outside black holes. Likewise, they are significant elements in galactic & smaller scale jet models.

How well do "accepted" theories incorperate/model such dynamic electrical phenomena into their respective mathematical equations? a little? alot? not at all?

As noted above, it depends entirely on the specific situation. Sometimes not at all, sometimes a lot, sometimes in between.

Does electricity play any role in space besides making pretty "lights"? i.e. does it do any "work"?

It doesn't make any "pretty lights" that I am aware of, or any other kind of light for that matter. Electric currents of the "electricity style" are common in the solar system, and are built into models of the heliosphere, planetary magnetospheres & etc.

Does a flow of charged particles constitute "electricity"?

See the caveat at the top. No, a flow of charged particles definitely does not constitute "electricity". However, electricity is definitely a flow of charged particles. Electricity exists only in wires & circuits. Flows of charged particles exist in astrophysics.

Is an object, spaceprobe, asteroid, moon, planet able to collect a "charge"?

Yes, and it should not be "charge" in quotes. Spacecraft collect a real, net electric charge, and are routinely designed to deal with it.

Now, if you (Northwind) respond to each of these with a new list of questions the whole thing will get way to long to handle. I suggest you pick one or two of these points, as seems most important or significant to you, and ask only those questions. And put each question in a separate thread. This will allow things to remain reasonably uncomplicated, and not unreasonably long. In this post I am constrained by time, like anyone else, and so cannot fully answer any question, in order to at least partially answer all questions. The shotgun approach to Q&A is not conducive either to depth or understanding.

[Jeff Root]

Does electricity play any role in space besides making
pretty "lights"? i.e. does it do any "work"?

It doesn't make any "pretty lights" that I am aware of,
or any other kind of light for that matter.

Starlight and aurora. Both are light emitted by acceleration
of charged particles in collisions.

-- Jeff, in Minneapolis

[Jeff Root]

Does a flow of charged particles constitute "electricity"?

No, a flow of charged particles definitely does not constitute
"electricity". However, electricity is definitely a flow of
charged particles. Electricity exists only in wires & circuits.
Flows of charged particles exist in astrophysics.

Boy, is that ever a pointless distinction. A flow of charged
particles is called "electricity" if in wires and circuits, but
not elsewhere.

The dictionary I have relied on for the last 40 years, Webster's
New World Dictionary of the American Language, College Edition
(1964), says:

electricity n. 1. a form of energy generated by friction,
induction, or chemical change, and having magnetic, chemical,
and radiant effects: it is a property of the basic particles
of all matter, consisting of protons (positive charges) and
electrons (negative charges), which attract each other.
2. a) an electric current; stream of moving electrons: it sets
up a magnetic field of force through which it produces kinetic
energy. b) static electricity; charge of stationary particles:
it sets up a field of force having potential energy. 3. The
branch of physics dealing with electricity. 4. electric current
suplied as a public utility for lighting, heating, etc.

The American Heritage Dictionary of the English Language,
Third Edition (1992) which is part of Microsoft Bookshelf:

electricity noun
1. a. The physical phenomena arising from the behavior of electrons
and protons that is caused by the attraction of particles with
opposite charges and the repulsion of particles with the same
charge. b. The physical science of such phenomena.
2. Electric current used or regarded as a source of power.

My Radio Shack Dictionary of Electronics (1975) Doesn't have a
good 'definition' per se, but the entry says in part:

electricity-- The property of certain particles to posess a
force field.... Electricity can be further classified as static
electricity or dynamic electricity. Static electricity in its
strictest sense refers to charges at rest, as opposed to dynamic
electricity, or charges in motion. Static electricity is
sometimes used as a synonym for triboelectricity or frictional
electricity.

My high school physics textbook was "Physics - Second Edition"
by the Physical Science Study Committee, Educational Services,
Inc., published by D.C. Heath and Company (1965). The book is
divided into four major parts. Part IV is titled 'Electricity
and Atomic Structure'. While it is true that a large fraction
of that section of the book is about electric circuits, including
a chapter titled 'Electric circuits', it is all about electricity
as a physical phenomenon of nature.

-- Jeff, in Minneapolis

[Northwind]

Now, if you (Northwind) respond to each of these with a new list of questions the whole thing will get way to long to handle. I suggest you pick one or two of these points, as seems most important or significant to you, and ask only those questions. And put each question in a separate thread. This will allow things to remain reasonably uncomplicated, and not unreasonably long.

Good idea?

Here's my pick then.

Korjik is right, so I want to make sure the caveat is well understood. We should be talking about electric fields and electric currents, that's the jargon you will see in astrophysics. The word electricity will never appear in astrophysics, as it is engineering & technology jargon. That said, we also need to remember that electricity is an electric current, it just happens to be confined by wires. And that is an important point to remember, because the wires strongly confine electricity, and strongly affect its behavior. Electric currents in astrophysics do not behave like electric currents in electricity, because they are not confined & restricted in the same way.

Define Birkeland currents wrt electric currents in astrophysics? Obviously I understand there are no "wires" (as in copper/aluminum wires?) in space. And I'd like to hear your understanding behind what Birkeland currents are?

onto

But it is important to realize the electric currents of the type represented by electricity, namely a flow of charged particles which all have the same electric charge, are rare. In most cases, the current is charge neutral because there are no electric fields strong enough to promote significant charge separation. I am presuming you are interested in the kind of current I have mentioned here, a flow of like charged particles.

Understood, the question rises then, what happens when the "flow of charged particles" encounters a substantial electric(magnetic) field? say the Earths, Jupiter a comets?

Charge separation occurs? What happens to the flow?

The significance, not surprisingly, depends entirely on the specifics of the moment. In some cases, electric currents are irrelevant, if they even are there. In other cases, they are significant, and must be included in any physical model. As I mentioned above, flows of like charged particles are rare, but not altogether absent. These "electricity" style currents flow in the solar photosphere, and in the magnetosphere of Earth. They also flow in a circuit that connects the solid earth to the magnetosphere and solar wind

and I'd postulate the rest of the solar system.

This is the bit that I have trouble understanding, so why is this not taught this in educational facilities? Because if Earth does, by logical extension any planet/moon/rock with a magnetosphere/ionosphere/plasmasphere should be doing exactly the same thing? or is this where I'm getting confused? Does each and every planet/moon/rock have a different process?

Last one

Yes, and it should not be "charge" in quotes. Spacecraft collect a real, net electric charge, and are routinely designed to deal with it.

Agreed, so why couldn't a rock(asteroid/comet) do the same?

So why can't we "use" this electric charge? It's been proven via STS-75's TSS-1R mission that this is a viable means of generation and propulsion? Is it at the moment just a technological short coming? i.e. we can not store that amount of power? The debris surrounding the broken tether sure seemed interested in what we had nearly achieved, before the premature break from defective materials!

It is the way forward, imho

[Koliedrus]

Boy, is that ever a pointless distinction. A flow of charged
particles is called "electricity" if in wires and circuits, but
not elsewhere.

The dictionary I have relied on for the last 40 years, Webster's
New World Dictionary of the American Language, College Edition
(1964), says:

(snippage)

I can honestly say that that was the one of the kindest "LMAOROTF"'s that I've witnessed to date.

Lurking cloak, ACTIVATE!

[tusenfem]

Northwind
It would be good if you started reading an introductory book on plasma and space physics. I do not know your level of physics and mathematics, so it would be hard to give you correct pointers. Howver the following books are pretty good:
Lorrain & Corson, Electromagnetic Fields and Waves
Kivelson & Russell, Introduction to Space Physics
Goossens, Introduction to plasma astrophysics and MHD

Now to your points:

Define Birkeland currents wrt electric currents in astrophysics? Obviously I understand there are no "wires" (as in copper/aluminum wires?) in space. And I'd like to hear your understanding behind what Birkeland currents are?

Birkeland currents are magnetic field aligned currents in the (Earth's) magnetosphere, that create the aurora, and were called after Kristian Birkeland, who posited that electrical currents were responsible for the aurora. (I still have to find out whether he meant what are now called Birkeland currents, i.e. field aligned, or that he meant what is now called the westward electrojet, i.e. perpendicular currents. Have to start reading his scientific biography).

Charged particles connect themselves to magnetic fields, because of the Lorentz force that is acting. A charge moving at an angle wrt a magnetic field will experience a Lorentz force (VxB) perpendicular to the velocity and thus it gets bend around the field. In this way, when the magnetic field is strong enough, or when the plasma is magnetized, the magnetic field lines can be considered the wires in space. Definitely this is the case for the Birkeland currents.

Now, I am a purist, and only use Birkeland currents for magnetospheres. Other people like to use the term also for magnetic field aligned currents in other locations in space.

Understood, the question rises then, what happens when the "flow of charged particles" encounters a substantial electric(magnetic) field? say the Earths, Jupiter a comets? Charge separation occurs? What happens to the flow?

That all depends on the situation. First of all, ecnountering electric fields is rather tricky in space, but if plasma gets into an electric field it will be accelerated, electrons in one direction, ions in the other, and the charge separation that created the electric field will quickly be negated and the electric field will be gone.
However at the Earth there is mainly a magnetic field. If e.g. you look at the plasma in the Jovian magnetosphere arriving at Europa, or if you look at the plasma of the solar wind arriving at Earth, you will find that the flow will be slowed down and the plasma will be diverted around the object, just like in a fluid (that is why plasmas can often be described as oridinary fluids).
Now, the case inside the magnetosphere of the Earth is different. If you have plasma that comes from the tail and moves into the inner magnetosphere, the particles, that are tied to the magnetic field will start to gradient drift. This is a drift caused by the decreasing magnitude of the magnetic field of the Earth in the radial direction. Here the electrons will move one way and the ions will move in the other direction. There you get some sort of charge separation, by this effect, but it is in combination with all kinds of othere processes too, so there is no enormous charge build up, because the particles either rotate around the Earth, or they escape through the magnetopause.

[quote = Tim]The significance, not surprisingly, depends entirely on the specifics of the moment. In some cases, electric currents are irrelevant, if they even are there. In other cases, they are significant, and must be included in any physical model. As I mentioned above, flows of like charged particles are rare, but not altogether absent. These "electricity" style currents flow in the solar photosphere, and in the magnetosphere of Earth. They also flow in a circuit that connects the solid earth to the magnetosphere and solar wind

and I'd postulate the rest of the solar system.
[/quote]

There are various current systems and not all are connected. I would not go as far as to say that the circuit from the solar wind connects to the solid Earth, in a sense of currents. But ofcourse, if you want you can see the whole solar system as one big electrodynamically coupled system, which it is, but does that help? I don't think so, because it is too big to oversee.

This is the bit that I have trouble understanding, so why is this not taught this in educational facilities? Because if Earth does, by logical extension any planet/moon/rock with a magnetosphere/ionosphere/plasmasphere should be doing exactly the same thing? or is this where I'm getting confused? Does each and every planet/moon/rock have a different process?

Maybe you have not gone to the right school, it depends on what educational facilities you mean. If you mean highschool, I don't think it has a pace there, it is much too complicated. You need Maxwell's equations to understand and use correctly. If you mean university, yeah, at least in Holland, when you study (astro)physics you get electrodynamics, teaching you all about Maxwell's equations etc. You get a little plasma physics, but it is a choice topic, you cannot study all of physics, how nice would that be if you could. And then you have to specialize in planetary physics or space physics to learn all about magnetospheres and stuff, it is a highly specialized field of space physics.

Every body has its own processes from a group of possible processes. If there is no internal magnetic field you will have no reconnection with the solar wind. A good example is comparing Europa (no internal field) and Ganymede (strong internal field) in the Jovian system. This has significant influence, e.g. whether the plasma in the magnetosphere or in the solar wind (depending on which situation you look at) will reach the surface of the object or not. Then again, there is a difference for the flows, they can be super/sub sonic, they can be super/sub Alfvenic, etc. etc. You cannot make a general model, you have to look at each object separately. Naturally, you can make educated guesses for like objects in like systems, e.g. what happens at Europa will most likely also happen at Callisto, however you need to adjust the parameters.
Last one

Agreed, so why couldn't a rock(asteroid/comet) do the same?

I probably can and will. There is the charging of the moon by the passage through the Earth's magnetotail. However, the processes at small bodies are much more efficient (considering a satellite a small body) and the metal of the satellite is much easier to knock out an electron by UV radiation. It all depends on the circumstances. And a rock asteroid comet is much much larger, and thus has is much easier, if significant charge would build up, to draw opposite charge towards itself and be neutralized again.

So why can't we "use" this electric charge? It's been proven via STS-75's TSS-1R mission that this is a viable means of generation and propulsion? Is it at the moment just a technological short coming? i.e. we can not store that amount of power? The debris surrounding the broken tether sure seemed interested in what we had nearly achieved, before the premature break from defective materials!

Well, in the normal case the charges are not that big, so using them leads to no avail. However, using a tether, likt in the experiment, can work, letting is slide across the magnetic field of the Earth to generate an electric field in the tether of value (E = v x B). However, to get any usefull energie out of it, you have to have a very long wire, and that is rather cumbersome in space and you need to make sure it remains across the field and not along it, because if the tether is aligned with the magnetic field, nothing will happen. So, it is not just a technological shortcoming or defective material, it is more an interesting experiment for which the application is too cumbersome to be of any real use.

Ofcourse you could have loads of tethers hanging e.g. from the ISS, but that would make docking the space shuttle a heck of problem.

[korjik]

Boy, is that ever a pointless distinction. A flow of charged
particles is called "electricity" if in wires and circuits, but
not elsewhere.

The dictionary I have relied on for the last 40 years, Webster's
New World Dictionary of the American Language, College Edition
(1964), says:

electricity n. 1. a form of energy generated by friction,
induction, or chemical change, and having magnetic, chemical,
and radiant effects: it is a property of the basic particles
of all matter, consisting of protons (positive charges) and
electrons (negative charges), which attract each other.
2. a) an electric current; stream of moving electrons: it sets
up a magnetic field of force through which it produces kinetic
energy. b) static electricity; charge of stationary particles:
it sets up a field of force having potential energy. 3. The
branch of physics dealing with electricity. 4. electric current
suplied as a public utility for lighting, heating, etc.

The American Heritage Dictionary of the English Language,
Third Edition (1992) which is part of Microsoft Bookshelf:

electricity noun
1. a. The physical phenomena arising from the behavior of electrons
and protons that is caused by the attraction of particles with
opposite charges and the repulsion of particles with the same
charge. b. The physical science of such phenomena.
2. Electric current used or regarded as a source of power.

My Radio Shack Dictionary of Electronics (1975) Doesn't have a
good 'definition' per se, but the entry says in part:

electricity-- The property of certain particles to posess a
force field.... Electricity can be further classified as static
electricity or dynamic electricity. Static electricity in its
strictest sense refers to charges at rest, as opposed to dynamic
electricity, or charges in motion. Static electricity is
sometimes used as a synonym for triboelectricity or frictional
electricity.

My high school physics textbook was "Physics - Second Edition"
by the Physical Science Study Committee, Educational Services,
Inc., published by D.C. Heath and Company (1965). The book is
divided into four major parts. Part IV is titled 'Electricity
and Atomic Structure'. While it is true that a large fraction
of that section of the book is about electric circuits, including
a chapter titled 'Electric circuits', it is all about electricity
as a physical phenomenon of nature.

-- Jeff, in Minneapolis

Wether you consider it pointless or not, useage by physicists is to not use the term electricity when it isnt a circuit. The multiple definitions you presented are probably the reason why.

[Northwind]

Quote:
Originally Posted by Northwind View Post
Understood, the question rises then, what happens when the "flow of charged particles" encounters a substantial electric(magnetic) field? say the Earths, Jupiter a comets? Charge separation occurs? What happens to the flow?
That all depends on the situation. First of all, ecnountering electric fields is rather tricky in space, but if plasma gets into an electric field it will be accelerated, electrons in one direction, ions in the other, and the charge separation that created the electric field will quickly be negated and the electric field will be gone.
However at the Earth there is mainly a magnetic field. If e.g. you look at the plasma in the Jovian magnetosphere arriving at Europa, or if you look at the plasma of the solar wind arriving at Earth, you will find that the flow will be slowed down and the plasma will be diverted around the object, just like in a fluid (that is why plasmas can often be described as oridinary fluids).

So do electrons and Ions slow at the same rate?

Charged particles connect themselves to magnetic fields, because of the Lorentz force that is acting. A charge moving at an angle wrt a magnetic field will experience a Lorentz force (VxB) perpendicular to the velocity and thus it gets bend around the field. In this way, when the magnetic field is strong enough, or when the plasma is magnetized, the magnetic field lines can be considered the wires in space. Definitely this is the case for the Birkeland currents.

This is an area of space exploration we should be concentrating on!

[Jeff Root]

My high school physics textbook was "Physics - Second Edition"
by the Physical Science Study Committee, Educational Services,
Inc., published by D.C. Heath and Company (1965). The book is
divided into four major parts. Part IV is titled 'Electricity
and Atomic Structure'. While it is true that a large fraction
of that section of the book is about electric circuits, including
a chapter titled 'Electric circuits', it is all about electricity
as a physical phenomenon of nature.

Wether you consider it pointless or not, useage by physicists is to
not use the term electricity when it isnt a circuit.

You say that immediately after quoting my citation of
physicists using the term 'electricity' to refer to electric
phenomenae in general, whether part of a circuit or not.

And my citation is of usage not in some obsure article or
paper, by one researcher somewhere, but in a standard
high school physics textbook used in thousands of schools,
written by a committee of physicists who were professionals
in teaching college-level physics. It may not be an exciting
or groundbreaking textbook, but it is certainly standard,
conventional, non-controversial, and widely-accepted.

-- Jeff, in Minneapolis

[Jeff Root]

Wether you consider it pointless or not, useage by physicists is
to not use the term electricity when it isnt a circuit. The multiple
definitions you presented are probably the reason why.

Is that also why physicists do not use the term 'spin', for which
I find 18 definitions? Or 'length', for which I find 9 definitions?
Or 'distance', for which I find 13 definitions? Or 'time', for which
I find approximately 41 definitions? Or 'light', for which I find
approximately 25 definitions? Physicists would avoid using any
term that had multiple definitions, wouldn't they?

-- Jeff, in Minneapolis

[EDG]

You can point to dictionary definitions all you like, but the fact of the matter is that physicists don't talk about "electricity" in space - they talk about electric currents, electromagnetic fields, plasmas, and charged particles/ions.

[Tim Thompson]

Define Birkeland currents wrt electric currents in astrophysics? Obviously I understand there are no "wires" (as in copper/aluminum wires?) in space. And I'd like to hear your understanding behind what Birkeland currents are?

Well, tusenfem already gave a suitable answer. But I'll chime in anyway. Specifically, the Birkeland currents run along magnetic field lines that are open to the solar wind. At high latitudes, the Birkeland currents flow into the ionosphere on the night side, and into the ionosphere on the morning side. At lower latitudes this pattern is reversed. The circuit is closed in the ionosphere by field aligned Pederson currents (the common EU usage of "Birkeland current" for any field aligned current is improper, and does not reflect the usage of the science community). The circuit is assumed to be closed by currents flowing in the magnetosphere, which makes sense, but I don't know how well those currents are actually measured. The current carrier is usually electrons, and the common engineering protocol is used, so the direction of the current is opposite to the direction in which electrons move.

Understood, the question rises then, what happens when the "flow of charged particles" encounters a substantial electric (magnetic) field? say the Earths, Jupiter a comets? Charge separation occurs? What happens to the flow?

Charge separation commonly ocurs, because it is easier to deflect less massive electrons, than more massive protons. The result is a complicated array of current sheets & flux tubes, like the current that runs between Jupiter & Io, or the current sheets in Earth's magnetosphere. In the ionosphere of Earth, electric fields & currents are generated by the wind. The mass motion of the atmosphere forces the massive protons across magnetic field lines, while the lighter electrons are able to move along field lines.

This is the bit that I have trouble understanding, so why is this not taught this in educational facilities? Because if Earth does, by logical extension any planet/moon/rock with a magnetosphere/ionosphere/plasmasphere should be doing exactly the same thing? or is this where I'm getting confused? Does each and every planet/moon/rock have a different process?

It is tought, in all educational facilities that teach space physics or astrophysics. It is rarely tought in high schools for reasons already mentions by tusenfem, namely that there is no room for it, nor any sense in teaching it, in a high school curriculum. But anybody who studies astrophysics learns all of this. Atmospheric electricity is nicely covered in Richard Feynman's classic Lectures on Physics (vol II). The global electric circuit is well known to mainstream science (i.e., Harrison, 2004).

Last one

Yes, and it should not be "charge" in quotes. Spacecraft collect a real, net electric charge, and are routinely designed to deal with it.

Agreed, so why couldn't a rock (asteroid/comet) do the same?

They do. Dust grains are easily charged, both on the lunar surface, and in the interplanetary medium. Asteroids undoubtedly have net surface charges, if only because of UV induced ionization. The difference between the mainstream & EU are that in the EU way of seing things, the electric charge dominates the dynamics. In the mainstream view, the electric chrage is just one of many forces at work. Electric chraging does dominate the dynamics of dust in the solar system, but is inadequate to significantly affect the dynamics of more massive objects.

So why can't we "use" this electric charge? It's been proven via STS-75's TSS-1R mission that this is a viable means of generation and propulsion? Is it at the moment just a technological short coming? i.e. we can not store that amount of power? The debris surrounding the broken tether sure seemed interested in what we had nearly achieved, before the premature break from defective materials!

You probably could use it, but what for? No doubt one could obtain substantial voltages, but unfortunately small currents to go with them. Propulsion systems need both. Ion propulsion systems are based on electrostatic repulsion to drive ions like a rocket exhaust. Low thrust for long periods generates high speeds.

[Tim Thompson]

Boy, is that ever a pointless distinction.

I disagree, I think it is a pointed distinction. The word "electricity" is never used, for any reason, in the astrophysics discipline, except with reference to power supplies for instruments mounted on a telescope. So, some poor neophyte plows through the astrophysical literature, fails to find the word "electricity", and then loudly proclaims that astrophysicists never bother to study electric currents. The definitions from your books are all irrelevant, because as a matter of fact, astrophysicists never use the word in this context.

Proper use of language enhances clarity of communication. Improper use of language only makes things more confusing than they need to be. The use of the word "electricity" is needlessly confusing and should therefore be avoided.

[papageno]

It is tought, in all educational facilities that teach space physics or astrophysics. It is rarely tought in high schools for reasons already mentions by tusenfem, namely that there is no room for it, nor any sense in teaching it, in a high school curriculum. But anybody who studies astrophysics learns all of this.

Elements of plasma physics are also necessary in Solid State Physics, because the electrons in a metal can be well described as a gas of free (charged) particles. And we even get quantized oscillations of the charge density (plasmons).

The word "electricity" is never used, for any reason, in the astrophysics discipline ...

Nor is it used in Solid State Physics, not even for metals.
You won't find the word "electricity" as a technical term ever in any text.

[tusenfem]

So do electrons and Ions slow at the same rate?

Yes, because the slowing of the flow is done by magnetic pile up, and the electrons and ions are linked to the magnetic field.

This is an area of space exploration we should be concentrating on!

If you say so, start concentrating.
Better explain why and how though, for this concentrating.

[tusenfem]

Can we move the electricity discussion to the thread that discussed "electricity" please?

One can find lots of definitios, but as already stated by several researchers the term "electricity" is not used in XXXX-physics, because it is too general.