Leaky Box Model Research Articles

On the propagation of cosmic rays in the Galaxy

Cosmic ray propagation in the Galaxy is examined within the framework of the leaky-box model, whereby phenomenological aspects of diffusion and propagation are related to the physical properties of the interstellar medium. The model is parameterized by data on composition, spectra, spectral change as a function of energy, and cosmic ray particle lifetime. It is assumed that electrons and nucleons have a common source within the Galaxy (probably associated with supernova remnants). Lifetime data and leakage length are compared with radio synchrotron and gamma-ray data to establish a place of origin for cosmic rays observed at earth, i.e., at a radius of 0.5-1.0 kpc from earth. It is noted that if the escape length becomes energy independent, all nuclear spectra will flatten, while the electron spectrum remains unchanged.

The age distribution of galactic cosmic rays

The general solution for the distribution of ages for primary galactic cosmic rays is given for a class of steady-state, bounded models of cosmic-ray diffusion in the Galaxy. Both one-and threedimensional models are considered, with point sources and distributed sources. In all models, the age distribution, is approximately exponential for ages longer than the average age, although for shorter ages the distribution depends on the details of the model. The leaky-box model, with an exponential age distribution, is thus a good approximation to most diffusive models. It is shown that one-dimensional (‘disk’) models are consistent with both age and anisotropy data for galactic cosmic rays regardless of whether production takes place near the galactic center or throughout the disk.

The nuclear composition of cosmic rays at their source in a closed galaxy

A MAIN objective of current theories of the galactic origin of cosmic radiation has been to explain the observed nuclear composition in terms of a source composition and spallation processes occurring during the propagation from the sources to the Solar System. The so-called leaky-box model can explain the observed composition only if the cosmic rays are assumed to escape from the galaxy after having traversed a few g cm−2 of interstellar gas, but has trouble explaining the flux of primaries of large airshowers. These very energetic nuclei are then assumed to be of extragalactic origin, as our own Galaxy cannot contain them long enough to build up the flux to the observed value and to assure even a moderate degree of isotropy.