2
$\begingroup$

If charged particles flow through non-magnetised space will they form Birkeland current? Or can such currents only form along existing magnetic field lines?

Part of the reason I ask is this:

http://galileo.phys.virginia.edu/classes/252/rel_el_mag.html

Depending on the frame of reference, there is no difference between electrical and magnetic forces, they are really the same thing? Would charged particles in space be capable of inducing their own 'magnetic' field and spontaneously self organizing into a Birkeland current?

$\endgroup$
  • $\begingroup$ @heather My point was not that I personally wanted to know what they are, but to point out that the question could be made more accessible by providing a basic explanation of its context and the terminology used. Indeed, if the question had included the definition of such a current along a field line, it would have been apparent that it is rather non-sensical to ask if they can exist without field lines. $\endgroup$ – ACuriousMind Jul 26 '16 at 14:09
  • $\begingroup$ Not much point in giving a definition that answers the question; the definition may not quite be correct. I've added some information about relativity and the connection between electrical and magnetic fields. $\endgroup$ – user2800708 Jul 26 '16 at 16:56
  • $\begingroup$ @user2800708 - Birkeland currents are not a special type of current, other than that they are specifically associated with the terrestrial auroral regions. The picture came about because early observations had very low resolution, so the data was consistent with this circuit-like cartoon. While it is true that there are large regions of average current like this, a more realistic idea would be one with many smaller-scale currents that are temporally limited (e.g., think of transient filaments of current). $\endgroup$ – honeste_vivere Jul 27 '16 at 12:20
2
$\begingroup$

According to this website,

A Birkeland current is a set of currents that flow along geomagnetic field lines connecting the Earth’s magnetosphere to the Earth's high latitude ionosphere.

These then are driven by solar wind in the Earth's magnetosphere.

Birkeland currents are caused by the movement of plasma perpendicular to the magnetic field. They can also be created in the laboratory by multi-terawatt pulsed power generators. The term Birkeland current also commonly refers to electric currents in other planet's ionospheres that follow magnetic field lines. The term can also be used to refer to any field aligned electric current in space.

So it seems (though I'll be looking into it more) that they can only form on specific magnetic field lines.

Fun fact: small-scale variations in these currents produce the Aurora borealis and australis once the currents reach the upper atmosphere. Not related at all, but cool.

Hope this helps!

Another website that has more information is this one.

.

$\endgroup$
  • 1
    $\begingroup$ Please try not to link explictly mobile versions of websites, it is very annoying for a desktop user to be presented with a mobile site, while the site will almost always automatically switch from the desktop to mobile version if a mobile device accesses it. $\endgroup$ – ACuriousMind Jul 26 '16 at 14:13
  • $\begingroup$ @ACuriousMind, sorry! I answered this on an iPad. How should I fix that? $\endgroup$ – heather Jul 26 '16 at 14:17
  • $\begingroup$ I already edited it. How you would best get the non-mobile link from your iPad I can't really tell. $\endgroup$ – ACuriousMind Jul 26 '16 at 14:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.