Consider a toroidal magnetic field, as shown in Fig. 21.

(a) Show that the magnetic flux density along the axis of the torus is given by 

where B_a denotes the magnitude of B at the radial distance r = a.

(b) In what direction is the gradient drift associated with the radial variation of B_ϕ? Examine qualitatively the type of charge separation that occurs. Neglect the effect of the magnetic field line curvature.

(c) If E denotes the induced electric field due to charge separation, in what direction is the E * B drift?

(d) Show that it is not possible to co nfine a plasma in a purely toroidal magnetic field, because of the gradient drift and the E * B drift.

Figure 21.

Transcribed Image Text:

B = Ba 818