Vertical structure of Galactic disk kinematics from LAMOST K giants

We examine the vertical structure of Galactic disk kinematics over aGalactocentric radial distance range of $R=5-15$ $\rm{kpc}$ and up to $3$$\rm{kpc}$ away from the Galactic plane, using the K-type giants surveyed byLAMOST. Based on robust measurements of three-dimensional velocity moments, awobbly disk is detected in a phenomenological sense. An outflow dominates theradial motion of the inner disk, while in the outer disk there exist alternateoutward and inward flows. The vertical bulk velocities is a combination ofbreathing and bending modes. A contraction-like breathing mode with amplitudesincreasing with the distance to the plane and an upward bending mode dominatethe vertical motion outside $R_0$, and there are reversed breathing mode andbending mode at $R<R_0$, with amplitudes much smaller than those outside $R_0$.The mean azimuthal velocity decreases with the increasing distance to theplane, with gradients shallower for larger $R$. Stars in the south disk arerotating faster than stars in the north. The velocity ellipsoid orientationdiffers between different $R$: in the range of $5<R<9$ $\rm{kpc}$, the gradientof the tilt angle with respect to $\arctan(Z/R)$ decreases from $\sim0.83$ forthe inner disk to $\sim0.52$ for the outer disk; within $9<R<15$ $\rm{kpc}$,the tilt of velocity ellipsoid deviates from vertical antisymmetry. A clearflaring signature is found for both north and south disks based on the observedvertical structures of velocity ellipsoid.