Toroidal equilibrium: general considerations

From QED

(Freidberg p. 75)

B_p only

The plasma will not be in equilibrium due to the Hoop Force and the Tire Tube Force. These forces can be complensated in two ways:
1) A perfectly conducting shell. Since plasma expansion will compress B_p, an equilibrium will be achieved once the plasma moves outward from its initial position. Doesn't really work practically because the skin time of relevant metals is too short compared to experimental time scales.
2) A vertical field can be (and is) used to create and inward force. This can work quite well.
Both stabilization methods are moot as a plasma with purely poloidal field is instantly torn to shreds by bloodthirsty MHD instabilities. (Energy principle)

B_t only

From EM, we know that a solenoid bent into a torus yields . Thus the magnetic pressure on the inside of the torus will be significantly greater than the pressure on the outside.
Note that this force can not be contained by a conducting shell. Purely toroidal B lines can just slip around the expanding plasma. They are not forced into the conductor like in the purely poloidal case.