engleski

Forbush decreases associated to Stealth Coronal Mass Ejections

Interplanetary coronal mass ejections (ICMEs) are structures in the solar wind that are the counterparts of coronal mass ejections (CMEs) at the Sun. It is commonly believed that enhanced magnetic fields in interplanetary shocks and solar ejecta as well as the increased turbulence in the solar wind sheath region are the cause of Forbush decreases (FDs) representing decreases of galactic cosmic ray (GCR) intensities. Recently, stealth CMEs i.e.~CMEs with no apparent solar surface association have become a subject in recent studies of solar activity. Whether all of such stealth CMEs can drive a FD is difficult to investigate on the basis of neutron monitor NM measurements because these measurements not only reflect the GCR intensity variation in interplanetary space but also the variation of the geomagnetic field as well as the conditions in the Earth atmosphere. However, together with single detector counters from spacecraft instrumentation with a counting statistic simillar to the one of NMs allows allows the investigation of such small FDs. This work has been supported in part by Croatian Science Foundation under the project 6212 „Solar and Stellar Variability“ and by MZOS/DAAD bilateral project CORAMOD.

coronal mass ejections ; galactic cosmic rays ; Forbush decreases

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