The basic momentum-balance equation that is used to infer local
values of the momentum diffusivity () from measurements of
the rotation speed is []

Generally the densities and rotation frequencies are measured, the
torque densities are calculated from a beam code, and the equation is
solved for . The magnitude of the convection term
is somewhat arbitrary--the choice made in Eq. 12 is
that each ion convected across a flux surface carries with it the
local rotation speed. The turbulence which actually drives
cross-field transport might well impose a different multiplier. The
terms are the radial fluxes of each ion species, which are
determined separately from the particle continuity equation. The
assumption has been made that all the ions rotate at the same rotation
speed, which may not be valid in all regimes []. Ripple
damping is neglected.

Fri Jul 11 15:18:44 EDT 1997