Speaker
Description
Galactic cosmic rays (GCRs) are charged particles with extremely high energies originating from outside the heliosphere. Their passage through the solar wind is affected by many long and short term factors, including transient structures such as coronal mass ejections (CMEs). The short term decrease in GCR flux caused by CMEs, and observed by charged particle detectors on spacecraft and ground-based neutron monitors is called a Forbush decrease (FD). FDs have a varied and complex profile, often showing a 2-step decrease corresponding to the structure of the CME – the first decrease corresponding to the shock and turbulent sheath region, and the second caused by reduced radial transport into the magnetic cloud structure. Current analytic and numerical models of this phenomenon have considered diffusion through the shock or into the magnetic cloud as separate processes, but have not been applied to realistic, 3-dimensional CME field geometries. We present progress in combining magnetohydrodynamic simulations of CMEs and background solar wind with full-orbit test particle simulations to reproduce the entirety of a 2-step FD, and to gain a greater understanding of how energetic particle observations can be used to infer global structure of CMEs.
