“…The value of j x has, in principle, to be obtained from Ohm's law, which explicitly expresses the plasma model. But, in reality, the fact that the equilibrium equation ( 6) prescribes the jOJ>*) form for the functional dependence of the current density is sufficient to conclude that, in the linear approximation, (10) Actually, the functional dependence jj (^0) implies the cylindrical symmetry of this function, which is incompatible with the angular dependence of the other terms in Eq. (9).…”