1. NAME AND TITLE
LUIN-II: Analytical Straight-Ahead Transport Code SystemCalculation of Cosmic-Ray
Spectra, Fluxes and Ionization in the Earth's Atmosphere.
U.S. Health and Safety Laboratory, New York.
U.S. Department of Energy, Environmental Measurements Laboratory, New York.
3. CODING LANGUAGE AND COMPUTER
FORTRAN IV; CDC 6600.
4. NATURE OF PROBLEM SOLVED
LUIN calculates secondary particle fluxes and resulting ionization produced in the earth's atmosphere by galactic cosmic rays as well as spectra which are a function of zenith angle and energy. It takes into account altitude above the earth's surface, geographical location, atmospheric temperature and solar activity. Absorption and production cross sections are assumed to be independent of energy, and in solving the Boltzmann equations, the straight-ahead approximation is used. Also, the shape of all secondary hadron spectra are assumed to be identical when resulting from a collision at a given energy.
LUIN-II contains changes and improvements, such as an improved representation of the
stopping power which includes the effect of straggling; variable quadrature for calculating fluxes
and ionizations from doubly-different spectra; variable density structures which better reflect the
effect of changes in atmosphere temperature, the curvature of the earth, and the dependence of the
cut-off rigidities of zenith and azimuth.
5. METHOD OF SOLUTION
Passow and Alsmiller have obtained a solution to the Boltzmann equation in the straight-ahead
approximation with constant cross sections and with certain other restrictions on particle emission
spectra in-flight decay and charged particle stopping, for an incident flux homogeneous energy and
anglei.e., for a Green's function from which solutions of other kinds can be obtained by numerical
integration over space and angle. The resulting Green's functions are integrated over the primary
galactic spectra to yield the desired quantities. Muon spectra are obtained from the pion spectra
also in the straight-ahead approximation.
6. RESTRICTIONS OR LIMITATIONS
The underlying theory is invalid below about 100 MeV for hadrons. Muons are followed to 10
MeV. The upper limit of validity is not really known, but sea-level hadron spectra at energies of
40 TeV have been shown to be within about 20% of experiment.
7. TYPICAL RUNNING TIME
No study has been made by RSIC of typical running times for LUIN-II.
8. COMPUTER HARDWARE REQUIREMENTS
LUIN-II is operable on the CDC 6600 computer.
9. COMPUTER SOFTWARE REQUIREMENTS
A FORTRAN IV compiler is required.
a. Included in the documentation:
K. O'Brien, "LUIN, A Code for the Calculation of Cosmic Ray Propagation in the Atmosphere," EML-338 (February 1978).
b. Background information:
K. O'Brien, "LUIN, A Code for the Calculation of Cosmic Ray Propagation in the Atmosphere," HASL-275 (May 1973).
C. Passow, "Phenomenologische Theorie zur Berechnung einer Kaskade aus schweren Teilchen (Nukleonenkaskade) in der Materie," DESY Notiz A 2.85 (1962).
F. S. Alsmiller, "A General Category of Soluble Nucleon-Meson Cascade Equations," ORNL-3746 (1965).
11. CONTENTS OF CODE PACKAGE
Included are the referenced document and one (1.2MB) DOS diskette which contains the source
codes and data, plus output from the sample problem.
12. DATE OF ABSTRACT
October 1975; revised September 1982.
KEYWORDS: STRAIGHT-AHEAD; COSMIC RAYS; SPACE RADIATION