  Propagation of Galactic cosmic rays (CR) in the interstellar medium (ISM) is
among the unsolved problems in particle astrophysics. Interpretation of CR
spectrum and composition measurements and their possible link to dark matter
crucially relies on our understanding of CR propagation in the Galaxy. Several
air shower experiments have measured a significant anisotropy of CRs in the TeV
to PeV energy range. These observations hint to a complicated overlap of more
than one cause: from the distribution of the CR sources in the Milky Way to the
nature of such sources, from the turbulence properties of interstellar plasmas
to the inhomogeneous nature of the interstellar medium. Coherent magnetic
structures such as the heliosphere greatly influence the CR arrival direction
distribution. It is necessary to account for and remove the heliosphere's
distortion effects if we want to determine the pristine CR arrival direction
distribution in the local interstellar medium (LISM), the environment
surrounding the solar system up to the distance of particle mean free path. The
recent availability of accurate all-sky maps of CR arrival direction
distribution and the latest advancements in heliospheric modeling, make it
possible to infer the CR pitch angle distribution in the LISM using a Liouville
mapping technique. With the interstellar CR distribution, we can study the
global characteristics of CR diffusion, tap into the properties of interstellar
plasma turbulence, test the recent and local CR source hypothesis, and whether
clumps of dark matter have a role in the observed CR observations. The study
can lead to developments aiming to a better understanding of the heliosphere,
particularly the boundary region with the ISM, and additional constraints on
the LISM properties.
