MHD simulations of meso-scale processes in an ICME-like Magnetic Flux Rope

Coronal Mass Ejections (CMEs) are among the main drivers of geomagnetic storms. 
The intensity of such storms is related to both the amplitude, coherence
and orientation of the magnetic field embedded in the magnetic cloud carried by
the CME, which can be often identified as a Magnetic Flux Rope (MFR).

During their propagation in the Heliosphere, MFRs are subject
to meso/small-scale processes such as magnetic reconnection and interaction with
turbulent fluctuations. The latter arise from solar wind turbulence,
but also include the turbulent sheath region which can form behind the
interplanetary shock driven by the CME.
These processes are difficult to capture in global numerical simulations of
CMEs and are possibly responsible for the rather small magnetic
correlation lengths which have been estimated for magnetic clouds, as short as a few tenth of AU.

We present a new numerical approach that exploits a lagrangian reference frame
to follow the evolution of a MFR via a high-resolution, 2.5D, visco-resistive 
MHD code implementing spherical expansion (Expanding Box Model).
In particular, we simulate the evolution of a low-beta MFR immersed in a
turbulent medium and study the resiliency of the magnetic structure as a
function of the amplitude and correlation length of the surrounding turbulence.
We present preliminary results using different proxies to estimate the evolution
of MFR coherence and helicity.