  We investigate the dynamics of self-gravity wakes in dense planetary rings.
In particular, we examine how the pitch angle of self-gravity wakes depend on
ring parameters using N-body simulations. We calculate the pitch angles using
the two-dimensional autocorrelation function of the ring surface density. We
obtain the pitch angles for the inner and outer parts of the autocorrelation
function separately. We confirm that the pitch angles are 15 to 30 degrees for
reasonable ring parameters, which are consistent with previous studies. We find
that the inner pitch angle increases with the Saturnicentric distance, while it
barely depends on the optical depth and the restitution coefficient of ring
particles. The increase of the inner pitch angle with the Saturnicentric
distance is consistent with the observations of the A ring. The outer pitch
angle does not have the clear dependence on any ring parameters and is about 10
- 15 degrees. This value is consistent with the pitch angle of spiral arms in
collisionless systems.
