Open AccessDecay of interplanetary coronal mass ejections and Forbush decrease recovery times
Author(s) -
Penna Robert F.,
Quillen Alice C.
Publication year - 2005
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004ja010912
Subject(s) - coronal mass ejection , physics , interplanetary spaceflight , forbush decrease , astrophysics , cosmic ray , solar wind , radius , astronomy , nuclear physics , plasma , computer security , computer science
We investigate the relation between Forbush cosmic ray decrease recovery time and coronal mass ejection transit time between the Sun and Earth. We identify 17 Forbush decreases from ground‐based neutron count rates between 1978 and 2003 that occur during the same phase in the solar cycle and can be associated with single coronal mass ejections (CMEs) in the SOHO LASCO CME Catalog or previously published reports and with specific interplanetary coronal mass ejections (ICMEs) crossing the vicinity of Earth. We find an anticorrelation between Forbush recovery times and CME transit time that contradicts the predictions of simple cosmic ray diffusive barrier models. The anticorrelation suggests that the decay rate of ICMEs is anticorrelated with their travel speed. Forbush recovery times range from seven times the transit time for the fastest disturbance to a fifth the Sun‐Earth transit time for the slowest. To account for the large range of measured recovery times, we infer that the slowest disturbances must decay rapidly with radius, whereas the fastest ones must remain strong. The longest recovery times suggest that the fastest disturbances in our sample decayed less rapidly with radius than the ambient solar wind magnetic field strength.