We perform numerical simulations of a stellar galactic disk with initial conditions chosen to represent an unrelaxed population which might have been left following a merger .
Stars are unevenly distributed in radial action angle , though the disk is axisymmetric .
The velocity distribution in the simulated Solar neighborhood exhibits waves traveling in the direction of positive v , where u,v are the radial and tangential velocity components .
As the system relaxes and structure wraps in phase space , the features seen in the uv -plane move closer together .
We show that these results can be obtained also by a semi-analytical method .
We propose that this model could provide an explanation for the high velocity streams seen in the Solar neighborhood at approximate v in km/s , of -60 ( HR 1614 ) , -80 ( 1 ) , -100 ( Arcturus ) , and -160 ( 22 ) .
In addition , we predict four new features at v \approx -140 , -120 , 40 and 60 km/s .
By matching the number and positions of the observed streams , we estimate that the Milky Way disk was strongly perturbed \sim 1.9 Gyr ago .
This event could have been associated with Galactic bar formation .