The coupling of the ionosphere and magnetosphere can be understood by examining the field-aligned currents passing between the two. In his treatment of the shielding of the inner magnetosphere, Vasyliunas [1972> developed a mathematical formalism for representing this coupling by a pseudo Ohm's law. All the effects of the magnetospheric plasma are comprised in an equivalent Hall conductivity that is determined by the assumed ion density distribution. In this paper, an alternate derivation of this formalism is presented in which, unlike the original derivation, the kinematics of the ions do not enter at all. This underscores the importance of a strong assumption upon which the method rests; that is, the ion distribution is assumed to be time stationary. However, there is nothing in the model to insure that the physical drifts of the ions do indeed satisfy the requirement. This places severe restrictions on the proper use of the formalism and implies that its results cannot be assumed to be correct in the absence of extensive a posteriori analysis. ¿American Geophysical Union 1992