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Galactic Cosmic Ray Intensity Response to Interplanetary Coronal Mass Ejections/Magnetic Clouds in 1995 - 2009
journal contributionposted on 2023-05-17, 09:50 authored by Richardson, IG, Hilary Cane
We summarize the response of the galactic cosmic ray (CGR) intensity to the passage of the more than 300 interplanetary coronal mass ejections (ICMEs) and their associated shocks that passed the Earth during 1995 – 2009, a period that encompasses the whole of Solar Cycle 23. In ∼80% of cases, the GCR intensity decreased during the passage of these structures, i.e., a “Forbush decrease” occurred, while in ∼10% there was no significant change. In the remaining cases, the GCR intensity increased. Where there was an intensity decrease, minimum intensity was observed inside the ICME in ∼90% of these events. The observations confirm the role of both post-shock regions and ICMEs in the generation of these decreases, consistent with many previous studies, but contrary to the conclusion of Reames, Kahler, and Tylka (Astrophys. J. Lett. 700, L199, 2009) who, from examining a subset of ICMEs with flux-rope-like magnetic fields (magnetic clouds) argued that these are “open structures” that allow free access of particles including GCRs to their interior. In fact, we find that magnetic clouds are more likely to participate in the deepest GCR decreases than ICMEs that are not magnetic clouds.
Publication titleSolar Physics: A Journal for Solar and Solar-Stellar Research and The Study of Solar Terrestrial Physics
Department/SchoolSchool of Natural Sciences
Place of publicationNetherlands
Rights statementCopyright 2011 Springer Science+Business Media B.V.