Magnus force with inviscid flow

[flyers]

I am taking an introduction to fluids class and the topic of the magnus force came up. The effect of the magnus lift force on an object moving through a viscid flow makes sense to me, but the problem is that the professor also mentioned that there is also magnus lift when a ball rotates through inviscid flow. This doesn't make sense to me since there is slipping between the fluid particles and the rotating ball. How could the rotation of the ball affect the fluid in this case.

http://en.wikipedia.org/wiki/Magnus_effect

 

[Valerie Park]

The Magnus effect is a phenomenon in which a spinning object (such as a ball) creates a force perpendicular to its direction of motion. In the case of inviscid flow, the effect is due to the pressure difference created between the sides of the ball due to its rotation. This pressure difference causes an imbalance in the lift force generated on either side of the ball, resulting in a net lift force that acts perpendicular to the direction of motion. The magnitude of this lift force is proportional to the rate of spin and the velocity of the object.