Sudjelovanje na online XVIIth Hvar Astrophysical Colloquium – “The Sun and Heliosphere” s priopćenjem D. Maričić, F. Šterc, M. Dumbovic, D. Roša, D. Hržina, I. Romštajn: Isolated Earth-Impacting Interplanetary Coronal Mass Ejections and corresponding Galactic Cosmic Ray Flux Variations
Isolated Earth-Impacting Interplanetary Coronal Mass Ejections and corresponding Galactic Cosmic Ray Flux Variations
D. Maričić, F. Šterc, M. Dumbovic, D. Roša, D. Hržina, I. Romštajn
One of the main factors responsible for the variability of Forbush decreases (FD) are different interplanetary transients origination from different solar sources related to them. In this study we examine the influences of different parts of the isolated Earth directed interplanetary coronal mass ejections (ICMEs) on the associated Forbush decrease (turbulent sheat, TS, and magnetic obstacle, MO). We use the sample of isolated Earth-impacting interplanetary CMEs (ICMEs) that cover the period from January 2008 to August 2014, published in Maričić et al. (2020). According to the CME origin with active region and filament eruptions, the events in this study were separated into three subsets: active region (AR) CMEs, disappearing filament (DSF) CMEs, and stealthy CMEs. We analyse variations of cosmic-ray flux caused by TS and MO parts of the corresponding ICME for three subsets of CMEs. We find two different linear relations between FD magnitude caused by the TS and the MO ICME parts (both with very high correlations of cc >0.9), for DSF/stealthy ICMEs and for AR ICMEs. In addition, for all three types of CMEs we estimated that the TS related FD magnitude is highly correlated with the maximum of the flow speed and magnetic field strength in the TS (all show very high correlations of cc ~0.8 and cc ~0.82). Such correlation was not found for MOs related FD magnitude. This suggests that these AR type of ICMEs are formed in different magnetic field configurations than the DSF and stealthy type ICMEs.