Dynamical interstellar medium with Gaia and ground-based massive
  spectroscopic stellar surveys
  The ongoing Gaia mission of ESA will provide accurate spatial and kinematical
information for a large fraction of stars in the Galaxy. Interstellar
extinction and line absorption studies toward a large number of stars at
different distances and directions can give a 3-dimensional distribution map of
interstellar absorbers, and thus reach a similar spatial perfection. Under
certain morphologies (e.g. geometrically thin absorption curtains) one can
infer a complete velocity vector from its radial velocity component and so
obtain a dynamical information comparable to stars. But observations of a large
number of stars at different distances are needed to determine the location of
the absorption pockets. Therefore, techniques to measure interstellar
absorptions towards (abundant) cool stars are needed.
  A complex mix of colliding absorption clouds is found in the Galactic plane.
Thus, one would wish to start with deep observations to detect the weak, but
simpler interstellar absorptions at high Galactic latitudes. Finally,
interstellar atomic line absorption studies toward cool stars in the optical
are largely limited to Sodium and Potassium doublets, not covered by many
surveys, including Gaia. Diffuse interstellar bands can give the same type of
information as interstellar atomic absorption lines. A combination of both may
also point to differences in dynamics of different components of the
interstellar medium. In particular, the Gaia DIB at 862 nm can be used to build
absorption maps, as already demonstrated by RAVE. Additionally, several
ground-based surveys (e.g APOGEE, Gaia-ESO and Galah) are upgrading this
approach. The use of this new information can change our understanding in many
areas (e.g. determination of membership of stars in clusters, studies of a few
Myr old supernova remnants and investigations of Galactic fountains).
