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Title: A robust method for handling low density regions in hybrid simulations for collisionless plasmas

A robust method to handle vacuum and near vacuum regions in hybrid simulations for space and astrophysical plasmas is presented. The conventional hybrid simulation model dealing with kinetic ions and a massless charge-neutralizing electron fluid is known to be susceptible to numerical instability due to divergence of the whistler-mode wave dispersion, as well as division-by-density operation in regions of low density. Consequently, a pure vacuum region is not allowed to exist in the simulation domain unless some ad hoc technique is used. To resolve this difficulty, an alternative way to introduce finite electron inertia effect is proposed. Contrary to the conventional method, the proposed one introduces a correction to the electric field rather than the magnetic field. It is shown that the generalized Ohm's law correctly reduces to Laplace's equation in a vacuum which therefore does not involve any numerical problems. In addition, a variable ion-to-electron mass ratio is introduced to reduce the phase velocity of high frequency whistler waves at low density regions so that the stability condition is always satisfied. It is demonstrated that the proposed model is able to handle near vacuum regions generated as a result of nonlinear self-consistent development of the system, as well asmore » pure vacuum regions set up at the initial condition, without losing the advantages of the standard hybrid code.« less
Authors:
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Publication Date:
OSTI Identifier:
22382129
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Computational Physics; Journal Volume: 275; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ASTROPHYSICS; COLLISIONLESS PLASMA; COMPUTERIZED SIMULATION; CORRECTIONS; ELECTRIC FIELDS; ELECTRONS; IONS; LAPLACE EQUATION; MAGNETIC FIELDS; MOMENT OF INERTIA; NONLINEAR PROBLEMS; OHM LAW; PHASE VELOCITY; PLASMA DENSITY; PLASMA SIMULATION; WHISTLER INSTABILITY; WHISTLERS