1. NAME AND TITLE

LUIN-II: Analytical Straight-Ahead Transport Code SystemCalculation of Cosmic-Ray Spectra, Fluxes and Ionization in the Earth's Atmosphere.

2. CONTRIBUTORS

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.

10. REFERENCES

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.