  The determination of the chemical composition of interplanetary coronal mass
ejection (ICME) plasma is an open issue. More specifically, it is not yet fully
understood how remote sensing observations of the solar corona plasma during
solar disturbances evolve into plasma properties measured in situ away from the
Sun. The ambient conditions of the background interplanetary plasma are
important for space weather because they influence the evolutions, arrival
times, and geo-effectiveness of the disturbances. The Reverse In situ and MHD
APproach (RIMAP) is a technique to reconstruct the heliosphere on the ecliptic
plane (including the magnetic Parker spiral) directly from in situ measurements
acquired at 1 AU. It combines analytical and numerical approaches, preserving
the small-scale longitudinal variability of the wind flow lines. In this work,
we use RIMAP to test the interaction of an ICME with the interplanetary medium.
We model the propagation of a homogeneous non-magnetised (i.e. with no internal
flux rope) cloud starting at 800 km s-1 at 0.1 AU out to 1.1 AU. Our 3D
magnetohydrodynamics (MHD) simulation made with the PLUTO MHD code shows the
formation of a compression front ahead of the ICME, continuously driven by the
cloud expansion. Using a passive tracer, we find that the initial ICME material
does not fragment behind the front during its propagation, and we quantify the
mixing of the propagating plasma cloud with the ambient solar wind plasma,
which can be detected at 1 AU.
