engleski

Forbush decreases caused by expanding ICMEs: analytical model and observation

Forbush decreases are short-term depressions in the galactic cosmic ray (GCR) flux caused by interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs). Changes in GCR flux is of interest for many open questions regarding Earth weather/climate issues, as well as space travel, adding to the importance of understanding and modeling of Forbush decreases. In our study we focus on the depressions caused by ICMEs which do not drive shocks/sheaths and have smoothly rotating strong magnetic field (magnetic clouds). We consider initially empty magnetic cloud which fills up slowly with particles by perpendicular (radial) diffusion. We will discuss the feasibility of the diffusion-based analytical model with respect to observations, especially regarding the ICME expansion. We acknowledge the support of European Social Fond under the project ”PoKRet”, the support of Croatian Science Foundation under the project 6212 „Solar and Stellar Variability“and of MZOS/DAAD under the bilateral project “CORAMOD”.

coronal mass ejections ; galactic cosmic rays ; Forbush decreases

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