Coronal Mass Ejections are powerful eruptions on the Sun that propagate into the expanding solar wind and affect near-Earth space, both directly through their impact or indirectly through particle acceleration. Fundamental for space weather purposes is then to determine their arrival time and magnetic configuration at Earth along with their ability to accelerate particles. Global models of the solar wind indicate that the travel time of CME depends on speed and magnetic configuration relative to those of the solar wind streams they are crossing. Observations indicate that their geo-effectiveness depends strongly on their magnetic configuration relative to the Earth magnetosphere and on their kinetic energy. If, on the one hand, global models are necessary to describe the whole CME that spans a large angular and radial extent, on the other hand they cannot account for the turbulent dynamics characteristic of the solar wind and the CME itself, thus preventing a correct assessment of the drag exerted by the wind and of the local structure of the CME. While the first crucially determines the travel time from say, 0.1 AU to the Earth, the second may have a strong impact on the geo-effectiveness at Earth and on the scattering and acceleration of energetic particles. Indeed, one of the issues that are still less studied is the impact of mesoscale fluctuations and structures on the geo-effectiveness of the CME. The core of this project exploits a "local" approach to the numerical simulation of the CME propagation in the solar wind so as to allow tracking its dynamics and structure at mesoscales with the aim of pursuing three main objectives: (A) Improve current estimate of CME arrival time and speed, by determining the turbulent drag force from first principles under a variety of magnetic and flow configurations and by testing a forecasting tool with input from observations. (B) Assess the impact of the local structure of the CME on particle acceleration and scattering by mean of test particle simulations and observations of energetic particle enhancements and galactic cosmic ray variations. (C) Investigate the impact of the fluctuations and the CME structures at the mesoscales on the geo-effectiveness , i.e., on the occurrence of magnetic storms and magnetospheric substorms.

A data-driven analysis of energetic protons will be performed by the team to obtain the SEP, ESP and FD features, which will then be compared with the simulated particle distributions. Observations will be also exploited to characterise turbulence (e.g. structure function, correlation length). Finally, it will be possible to provide a statistical assessment of the geoeffective IMF and solar wind conditions in terms of magnetic field topology and plasma parameters for the occurrence of magnetospheric-ionospheric disturbances, i.e., magnetic storms and magnetospheric substorms.