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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 (CRAY VERSION)
Catalogue identifier: AAQU_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 24(1981)37
Programming language: Fortran.
Computer: CRAY-1.
Operating system: CTSS ON CRAY, LTSS ON 7600.
Word size: 64
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.

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.