Light element abundance
Overabundance of Li, Be and B due to spallation. Medium and heavy nuclei fragment in nuclear collisions and remains are almost always Li, Be or B.
Quantitative analysis is complicated… requires collision X-sections for various processes … and relative abundances seem to change with energy.
Notes:
The overabundance of light elements in the Universe is due to the fragmentation of the medium and heavy nuclei, the remains of which are almost always Li, Be and B.
This fragmentation is called spallation.
A quantitative analysis of the effects of spallation on the abundance of cosmic rays is difficult however. We would need to know what all the collision cross-sections for the various processes involved are - it’s further complicated because the relative abundances (which we will take a look at later) seem to change with energy.