def sphere_bulk_velocity(halo):
    """
    Set the bulk velocity for the sphere.

    Parameters
    ----------
    halo : Halo object
        The Halo object to be provided by the HaloCatalog.

    """
    halo.data_object.set_field_parameter('bulk_velocity', halo.data_object.
        quantities.bulk_velocity(use_particles=True))
