engleski

Forbush decrease model for expanding CMEs (ForbMod)

Forbush decreases (FDs) can be used as one of the "signatures" of an ICME passage. An analytical diffusion-expansion FD model (ForbMod) was developed that is based on the widely used approach of an initially empty, closed magnetic structure (i.e. flux rope) that fills up slowly with particles by diffusion perpendicular to the magnetic field of the flux rope. In our approach the FD amplitude is not only determined by the diffusion process but also by the expansion of the flux rope. While the first process leads to a smaller amplitude the second one leads again to a larger effect. Remote CME observations and 3D reconstruction is used to constrain initial and boundary conditions. CME evolutionary properties are taken into account by incorporating the flux rope expansion. Several options of flux rope expansion are regarded as competing mechanism to diffusion, which can lead to different FD characteristics, and forward modelling is used to analyse flux rope expansion and further constrain the model. In testing the model, a number of spacecraft and planetary observation is utilised, including those by the Radiation Assessment Detector aboard the Mars Rover Curiosity. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk_odowska- Curie grant agreement No 745782.

coronal mass ejections, flux rope, forbush decreases

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