Evaluating the Loaded Layer-Cake Model as a Multi-Zone Framework for Galactic Cosmic Ray Spectra

The Loaded Layer-Cake Model (LLCM) provides a framework for interpreting the cosmic ray spectra by combining time-dependent acceleration, diffusion, and spallation processes within supernova shocks, stellar wind shells, and OB-superbubble environments. The model features three characteristic zones. The first is an acceleration zone with a common rigidity slope of −7/3 ± 0.02. It is followed by an interaction zone, where Kolmogorov-type turbulence induces a slope change of 1/3. Finally, a bubble zone dominated by lightning-driven magnetic wave fields steepens the spectrum by 5/3. Integration across these zones yields expressions that successfully reproduce AMS-02 observations for elements Z = 1–26. Despite successful fits, the many degrees of freedom and induced degeneracies among spallation parameters continue to constrain the consistency and physical validity of the results. Here, we present a computational evaluation of the LLCM to test its physical foundations and its ability to describe observed cosmic ray spectra. We also explore strategies for incorporating measurable properties, such as diffusion and spallation timescales derived from OB-association environments, to further constrain the model. Finally, we analyze lepton data and secondary-to-primary ratios to assess its broader applicability. These refinements test the physical basis of the LLCM, clarify its connection to OB associations, and evaluate its accuracy in reproducing galactic cosmic ray spectra.