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Manuscript Title: FPPAC: a two-dimensional multispecies nonlinear Fokker-Planck package.
Authors: M.G. McCoy, A.A. Mirin, J. Killeen
Program title: FPPAC (CDC VERSION)
Catalogue identifier: AAQU_v2_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 24(1981)37
Programming language: Fortran.
Computer: CDC-7600.
Operating system: CTSS ON CRAY, LTSS ON 7600.
Word size: 60
Keywords: Plasma physics, Two-dimensional, Multispecies, Implicit, Nonlinear, Fokker-planck, Kinetic model.
Classification: 19.8.

Nature of problem:
The complete nonlinear multispecies Fokker-Planck collision operator for a plasma in two-dimensional velocity space is solved. The operator is expressed in terms of spherical coordinates (v=speed, theta=angle between velocity and magnetic field directions, phi=azimuthal angle) under the assumption of azimuthal symmetry. Provision is made for additional physics contributions.

Solution method:
The Fokker-Planck equation is solved using finite differences. Spatial derivatives are approximated by central differences. Time-advancement is accomplished through either implicit operator splitting, an alternating direction implicit (ADI) algorithm, or fully implicit differencing. (In the latter case the user must supply his own nine- banded linear systems solver.) The Fokker-Planck coefficients and their derivatives are computed by expanding the distribution functions and the Rosenbluth potentials in Legendre series, and equating the respective series coefficients.

Restrictions:
The user must adjust the number of meshpoints in the two coordinate directions as well as the number of Legendre polynomials used to calculate the Fokker-Planck coefficients. Sufficient accuracy for most problems is attained on both the CRAY and 7600. However, double precision should be used on a 32-bit-word machine.