  In this paper we study the well-posedness of a simple model of boundary layer
for rotating fluids between two concentric spheres near the equator. We show
that this model can be seen as a degenerate elliptic equation , for which we
prove an existence result thanks to a Lax-Milgram type lemma. We also prove
uniqueness under an additional integrability assumption and present a
transparent boundary condition for such layers.
