The Pedersen component of the Lorentz force produces an acceleration
that is generally in the zonal direction in much of the dawn and dusk
sectors in the auroral oval. During disturbed conditions, as the neutral
flow begins to accelerate and the flow speeds increase, a balance
develops in the meridional direction between the Coriolis, curvature,
and pressure gradient forces, which are dominant in the lower
thermosphere. The gradient wind equation that describes this balance
predicts that the cyclonic flow on the dawn side is limited to the
so-called regular solution, which has a maximum value of twice the
geostrophic wind speed. The anticyclonic flow on the dusk side, on the
other hand, can satisfy either the regular or anomalous solution with a
transition at twice the geostrophic wind speed. The anomalous flow
solutions have wind speeds significantly greater than the transition
value, but are limited by the inertial wind value, i.e., the value that
corresponds to a balance between the curvature and Coriolis forces. The
analysis is carried out to show this result, which indicates that a
significant quantitative asymmetry is expected between the dawn- and
dusk-side flow, as is observed and has been shown in both observations
and a number of numerical modeling studies. Implications for the wind
distribution of perturbed pressure gradients and inertial instability
are discussed.