Describing a vector field

Question

Compare the vector field $G=(\frac{-y}{x^2+y^2},\frac{x}{x^2+y^2})$ along circle with fixed radius $r$ with the parametrization of a circle $\alpha = (r\cos \theta, r \sin \theta)$. Describe the field without solving for field lines. So if the radius is fixed we get $G=(\frac{-\sin \theta}{r}, \frac{\cos \theta}{r})$, what does this tell us about how the vector field is physically? A hint would be much appreciated.