Birkeland currents are also one of a class of plasma phenomena called a
z-pinch, so named because the
azimuthal magnetic fields produced by the current pinches the current into a filamentary cable. This can also twist, producing a helical pinch that spirals like a twisted or braided rope, and this most closely corresponds to a Birkeland current. Pairs of parallel Birkeland currents will also interact due to
Ampère's force law: parallel Birkeland currents moving in the same direction will attract each other with an electromagnetic force inversely proportional to their distance apart whilst parallel Birkeland currents moving in opposite directions will repel each other. There is also a short-range circular component to the force between two Birkeland currents that is opposite to the longer-range parallel forces.<a href="
https://en.wikipedia.org/wiki/Birkeland_current#cite_note-12"><span>[</span>12<span>]</span></a>
Electrons moving along a Birkeland current may be accelerated by a plasma
double layer. If the resulting electrons approach the speed of light, they may subsequently produce a
Bennett pinch, which in a magnetic field causes the electrons to spiral and emit
synchrotron radiation that may include
radio,
visible light,
x-rays, and
gamma rays.