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The simulated features of heliospheric cosmic-ray modulation with a time-dependent drift model. IV - The role of heliospheric neutral sheet deformationPrevious calculations with a time-dependent drift model revealed the model to be less successful in describing time-dependent modulation during periods of moderate to large solar activity. In this paper, it is argued that a major reason for this is that the previously used wavy heliospheric neutral sheet (HNS) description was based on an idealized HNS not subject to any spatial evolution while propagating radially outward. It is suggested that the deformation and compression of HNS wave peaks will lead to significant increases in the crossfield diffusion across these peaks (short-circuiting). The cosmic rays will effectively experience reduced tilt angles and therefore a reduction in the integrated HNS modulation effect between an observer and the heliospheric boundary. During periods of moderate to large solar activity these HNS deformation processes are progressively more frequent and should lead to a significant reduction in time-dependent modulation as predicted by drift models. Calculations done with radially propagating tilt angles that effectively decrease with radial distance give the expected reduction which improves the general description of modulation from 1987-1988.
Document ID
19930026510
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Le Roux, J. A.
(Maryland Univ. College Park, United States)
Potgieter, M. S.
(Potchefstroom Univ. for Christian Higher Education, South Africa)
Date Acquired
August 15, 2013
Publication Date
October 1, 1992
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 397
Issue: 2
ISSN: 0004-637X
Subject Category
Solar Physics
Accession Number
93A10507
Funding Number(s)
CONTRACT_GRANT: NAG2-627
Distribution Limits
Public
Copyright
Other

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