Algodoo

Well, it is a torus in 2D, and uses water not plasma, but the effect is cool.

Delete the center circle for a different effect.

No water / plasma is lost.

EDIT: Just so you know, if your water doesn't boil, you will see a very different effect, but still cool. If it does boil, the effect is arguably cooler.

EDIT2: To make water boil press ~ and type SPH.viscosity=6, to make water not boil type SPH.viscosity=1 (and press Enter each time). Try both out, or different values.