I forget what exactly prompted me to write to the Ask-a-Physicist page, but here was my submission (more-or-less):
I just today received a response to my inquiry, and would be interested to know what people thought about it...Okay, since you want to know, I'm 28 (almost 29), out of school (BA, 2001 from the University of Oregon). As a hobbyist I've been reading a lot of news releases lately about space, and have a slightly loaded question:
What role does electricity play in space? Does it play an organizing role, as some sources have suggested?
I will refer you to several items I believe are of interest to the discussion:
Firstly, from your own site:
http://helios.gsfc.nasa.gov/qa_gp_elm.html#maglines
http://helios.gsfc.nasa.gov/qa_gp_elm.html#magrev
http://helios.gsfc.nasa.gov/qa_gp_elm.html#stopmag
It appears that electric currents are the source of magnetic fields. Period.
If those are insufficient resources, I refer you to these others:
http://hyperphysics.phy-astr.gsu.edu/hb ... agfie.html
http://www-istp.gsfc.nasa.gov/Education/wmfield.html
http://www.who.int/peh-emf/about/WhatisEMF/en/
http://en.wikipedia.org/wiki/Electromagnetic_field
They appear to be unanimous in declaring that ONLY electric currents are responsible for magnetic fields, in accordance with Maxwell and Ampere (whether they be currents in wires, or electrons in lock-step around the nuclei of their "parent" atoms in permanent magnets, the positive charges being locked in place and the electrons free to move about; the curie point simply being where that lockstep breaks down and random chaotic motion of the atoms / electrons takes over).
Furthermore, it has been noted that magnetic fields can be used diagnostically in the lab for assessing electric currents, field strengths, etc.
http://en.wikipedia.org/wiki/Electric_c ... omagnetism
"Electric current produces a magnetic field. The magnetic field can be visualized as a pattern of circular field lines surrounding the wire.
Electric current can be directly measured with a galvanometer, but this method involves breaking the circuit, which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field associated with the current. Devices used for this include Hall effect sensors, current clamps, current transformers, and Rogowski coils."
This all then bears on my question about the universe. We know that the visible universe is 99.999% plasma, which is highly conductive. We also know that the raw electric force is orders of magnitude stronger than the gravitational force, where there are electrical goings on (currents, electric fields, etc.), and fall off more slowly with distance than the gravitational force at the same distances.
Several articles in particular that I'm interested in include:
http://www.astronomy.com/asy/default.aspx?c=a&id=4215
http://www.sciencedaily.com/releases/20 ... 221049.htm
http://www.sciencedaily.com/releases/19 ... 080925.htm
http://www.space.com/scienceastronomy/p ... 50301.html
It seems that astronomers are confused. They see magnetism everywhere, but rarely, if ever, have I seen mention of the electric currents (unambiguously noted above) that MUST be present to power them. Their world view apparently sees "hot gas" rather than plasma, and magnetic fields divorced from electric currents. Am I wrong in wondering whether many astronomers have failed to see what is plainly in front of them?
If magnetic fields are diagnostic for electric currents in the lab, why not in space? The laws of electricity and magnetism are suppsedly universal. Ergo, where we see magnetic fields in space (everywhere), must not we consider the possibility (nay probability bordering on certainty based upon definition) that electric currents are flowing there and doing the heavy lifting of organizing the structures seen thereabouts? (Other things that have been linked to "magnetic fields" include galaxy clusters; the THEMIS results RE: "magnetic flux tubes" carrying a 650,000 Amp current between the sun and Earth; the Double-Helix Nebula, etc. etc.)
I'd be interested in the opinion of Dr. Charles W. Smith, who authored several of the "Ask a Physicist" entries on the electricity / magnetism part of the site. He appears to "get it" about the relationship between the two.
Apologies if this e-mail was overly long... It's an interesting topic, and requires a few references to properly frame the question.
Regards,
~Michael Gmirkin
He makes a few interesting notes. He does seem to get it. Though I might quibble with his note about plasma "dragging" magnetic fields along with it... Any other points to ponder or corrections to be made?Dear Michael,
There is no doubt but that you "get it" and you understand what is being said about electricity and magnetism. All that is left is to find the root of your concern and address it.
First, a couple of things I think we all agree on:
1) Magnetic fields are due to currents. The currents can occur over vast scales, intermediate scales very easy for a human to grasp, or over very minute scales. Currents are just moving charge, and if there is a net motion of charge, there is a current.
2) Gravitational force seems to give structure to the universe and bind together what is bound on the largest of scales. There are several reasons why gravity dominates and not electric or magnetic fields. The first is that magnetic forces vary as the inverse of distance cubed, while the others vary as the inverse of distance squared, so magnetic forces are the shortest range of the three.
Another thing to consider is that electric forces can both attract and repel. A positive charge tends to become surrounded by negative charges. From a distance, they neutralize one another and no net charge is seen. In plasmas this is called Debye shielding, and over distances bigger than a surprisingly small distance (Debye length), one does not observe the buildup of charge. This tends to cancel electric forces at these distances.
Nothing neutralizes gravity. So gravity is left to have its way over the vast distances of space.
So, if magnetic fields exist in space where are the currents? There is more subtlety to this question than you may appreciate. The first point is that there are currents - there have to be currents to get magnetic fields. However, consider this: A current confined to a wire produces a magnetic field that fills the space around the wire. So we can measure magnetic fields everywhere, but the currents that produce them may be much more isolated.
Let's think about what creates a current. Two things cause currents to flow: separation of charge and electromotive force via Faraday’s Law. The latter can be used to create separation of charge, as when you charge a battery. Separation of charge in space can be accomplished, but it is difficult. Many of the currents that flow in space are the result of an electromotive force. When you consider that a conducting fluid such as a plasma will convect the magnetic field and carry it with the flow, it isn't hard to imagine that the magnetic field can be rapidly changing at any point in space and can become quite complex. So are the currents that support the fields.
In magnetospheric physics, there are two schools. One school attempts to understand the complex dynamics of the magnetosphere by specifying the currents and the other by way of the magnetic fields. If the currents are localized, we may not have spacecraft in the proper place to measure them. Since the magnetic fields fill space, it is more likely that we can study them, in an attempt to better understand the currents that produce them. Add to that the difficulties in measuring currents in space and you may begin to appreciate why so many people choose to address the magnetic fields and not the currents that produce them. However, the current approach has a strong following in magnetospheric physics.
You seem very well read, so let me recommend a book to you: Eugene Parker's "Conversations on Electric and Magnetic Fields in the Cosmos". It is very good and he tackles exactly the problem you pose. Gene is in many ways the father of modern space physics, and while he is now retired, he speaks and writes wonderfully. The book is excellent, but it is advanced.
I've offered you my prejudicial view of why people talk more about magnetic fields than the currents that produce them. One thing is true - you can't have one without the other. You need to decide which half of the pair will give you the information you need, and then decide how to get at it. It's a complicated subject, but you are headed in the right direction.
I hope that helps. Thanks for your question.
Charles W. Smith
for Cosmicopia
http://helios.gsfc.nasa.gov
Regards,
~Michael Gmirkin