Huh.

I do not recall ever reading or hearing about what is now the 'legends' version of the canon... that lightsabers form some kind of self recycling loop, in that manner.

...

But anyway, that also makes no sense in our real world physics.

It... still net expends energy to maintain plasma in a contained space.

Said plasma would want to basically explode outward in every direction, and a real world magnetic field would have to be stronger than that (real world) force, and ... also... it would be absurdly thermally hot that any wielder of a lightsaber would basically oven cook themselves within seconds of turning it on.

...

As of yet, nuclear fusion in a tokomak style, contained plasma loop... is still a net energy loss, and that is the closest real world equivalent to a 'self cohering plasma bolt' that I can think of...

Barring I guess 'ball lightning', maybe, which is theorerically proposed to maybe be some kind of naturally occuring instance of something similar, but to my knowledge, no one has ever like, made a ball lightning generator to test those theories.