Eve Ostriker is currently working intensively on several aspects of the interaction between cosmic rays and interstellar gas.  In particular, with collaborators she is (1) using MHD-PIC methods to study the interaction between streaming cosmic rays and partially-ionized gas, in  order to understand the transport of cosmic rays through atomic and molecular clouds in the  ISM, where damping of alfven waves by  ion-neutral collisions limits scattering; and (2) using a numerical two-moment cosmic rays fluid code to study the detailed distribution of cosmic  rays (both GeV and lower-energy) with ISM gas and magnetic fields from pc-to-kpc scales, as produced by simulations of the three-phase star-forming ISM.