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CME geometry in relation to cosmic ray anisotropy
Author(s) -
Bieber John W.,
Evenson Paul
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl51232
Subject(s) - cosmic ray , anisotropy , ejecta , physics , neutron monitor , astrophysics , magnetic cloud , magnetic field , shock (circulatory) , computational physics , geophysics , astronomy , solar wind , coronal mass ejection , supernova , optics , medicine , quantum mechanics
Strong enhancements of the cosmic ray anisotropy were observed before and during the January 1997 CME/magnetic cloud. From a multi‐station analysis of neutron monitor data, we conclude that “B × ∇ n ” drift is a primary source of CME‐related anisotropies for 5 GeV cosmic rays. Evolution of the cosmic ray density and density gradients is closely linked to magnetic properties of the ejecta, and provides information on the magnetic cloud and related features as they approach and pass Earth. Strong enhancement of the field‐aligned anisotropy was observed primarily during the 9 hours prior to shock arrival. If typical, this phenomenon should prove useful for space weather forecasting.