We consider a Ginzburg-Landau type functional on S-2 with a 6(th) order pot
ential and the corresponding selfduality equations. We study the limiting b
ehavior in the two vortex case when a coupling parameter tends to zero. Thi
s two vortex case is a limiting case for the Moser inequality, and we corre
spondingly detect a rich and varied asymptotic behavior depending on rile p
osition of the vortices. We exploit analogies with the Nirenberg problem fo
r the prescribed Gauss curvature equation on S-2.