# Can you create a powerful magnetic field out of confined circulating electrons only?

Would it be possible, regardless of how efficient it was to do something like this, or why you would actually do it, to generate a really powerful magnetic field simply by producing a cycling electric current with lots and lots of electrons, without any actual physical medium like a superconductor material that you would normally run the current through? I know that this sounds similar to particle accelerators and/or superconductors, but that isn't quite what I am imagining.

If you were out in near-vacuum of space and you could set up a loop where electrons whipped around very quickly, most likely under the influence of an external magnetic field that directed this, would the electrons on their own be able to generate a magnetic field, or would you need a magnet or a core material, as in an electromagnet, to activate or amplify the magnetic field somehow?

If you were able to collect enough electrons to be equivalent to say, the mass of the Earth, and you had a very large energy source, like the Sun, or a neutron star, that emitted a powerful enough magnetic field that you could somehow attenuate or direct, could you create a very powerful magnetic field that way?

If you were out in near-vacuum of space and you could set up a loop where electrons whipped around very quickly, most likely under the influence of an external magnetic field that directed this, would the electrons on their own be able to generate a magnetic field, or would you need a magnet or a core material, as in an electromagnet, to activate or amplify the magnetic field somehow?

Italics mine.

The electrons can be in a circular orbit due to a magnetic field which has to be continuously supplied.

The well known Bq/v=mv^2/r trajectory.

Their orbit cannot be self sustained. The minute the external field is stopped the electrons will follow a straight line.

As pointed out in the comments electrons can be manipulated in a medium , which is how electromagnets work.

Self sustained magnetic fields exist in plasmas, called magnetic cosmic plasmas. because they have been observed in the interstellar space and are studied in models of the sun. It is a whole field of study and research as one discovers by a search on the net.

Any current (flow of charges) produces a magnetic field, ragardless of if it is in a medium or not. $$\oint \vec B \cdot d \vec s = \mu_0 I$$ where $\vec B$ is the magnetic field and $I$ is the current. If the electrons are flying in a straight line, the magnetic field will be concentric circles around the current, like this:

At any point in space, you therefore have a magnetic field that is perpendicular to the current flow. To get a field similar to a bar magnet, you need a loop, and as you said already, without a conductor, you need a magnetic field to deflect the electrons.

That said, you can of course amplify the magnetic field by using an iron core for example. This basically just changes the value of $\mu_0$ to $\mu_r \mu_0$ and you end up with a stronger magnetic field. However, there still is a magnetic field even without that core ($\mu_0 \neq 0$).

About the question of the neutron star...I'm not sure why you would want to take the detour with the electrons if you say that object creates a magnetic field anyway. Also, consider that static magnetic fields drop with $\frac{1}{r}$ from a source.

• Thanks for the reply and the information - I only mentioned the neutron star as a potential 'energy or control' source for directing the electrons; of course as you say it already has a magnetic field, I shouldn't have confused the issue. Can you describe in a bit more detail, when you say "If the electrons are flying in a straight line, the magnetic field will be concentric circles around the current" - do you mean in a spiral around the entire 'line' of electrons, or around each individual electron orthogonal to it; how could I visualise it? – Phyneas Mar 5 '15 at 10:17
• You can actually do a simple experiment to visualize it: get a wire, hang it up over a table in a straight horizontal line and let some current flow through. Now, place a compass underneath it. You will find that the compass does not align with the wire, but instead always points at right angles to it. You can now try to follow one of the field lines by moving the compass in the direction it's pointing (in 3 dimensions): you'll find that magnetic field lines form closed circles around the conductor. Quite the opposite of electric field lines, they start and end at charges – ahemmetter Mar 5 '15 at 10:26
• Ahh, thanks very much for the clarification on that, I can visualise it now. On a general note, is there anything inherently inefficient or implausible about the above setup versus more traditional magnetic sources (superconduction, magnetars, electromagnets et cetera)? Is there any inherent benefit to confined vs unconfined, electrons on their own versus through a medium? – Phyneas Mar 5 '15 at 10:52
• Charges in a conductor follow the conductor without an external magnetic field. That is probably a great advantage. With free electrons, the only deflections would come from external electric and magnetic fields. The fields are the same of course, but it is arguably more practical to use conductors and insulators to control the flow of electrons rather than external, macroscopic fields. I dont see exactly where the advantage would be in your setup compared to a simple wire loop. – ahemmetter Mar 5 '15 at 10:55
• How would you manipulate those loops? You'd probably need an external field again. Also, stray fields and interaction with matter will make this very difficult – ahemmetter Mar 5 '15 at 11:14