Procedure: thm_part_dist_vels Purpose: Calculate bulk particle velocities from a structure array of particle distrubutions and store in a tplot variable. Arguments: DIST_ARR: An array of data structures as returned by one of the get_th?_p??? routines (or THM_PART_DIST_ARRAY). OUT_NAME: Name of tplot variable in which to store the velocities. See Also: THM_PART_DIST_ARRAY, V_3D Created by Bryan Kerr